7.6 Korrosion und Korrosionsschutz
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- 2019 (123) (entfernen)
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- Vortrag (73)
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- Forschungsbericht (3)
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- Deutsch (64)
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- Korrosion (43)
- Corrosion (32)
- Nichtrostender Stahl (11)
- Carbon steel (9)
- Deckschichtbildung (8)
- Gelartige Elektrolyte (7)
- Korrosionsschutz (7)
- KorroPad (6)
- Korrosionsprüfung (6)
- CCS (5)
Organisationseinheit der BAM
- 7 Bauwerkssicherheit (123)
- 7.6 Korrosion und Korrosionsschutz (123)
- 5 Werkstofftechnik (15)
- 5.1 Mikrostruktur Design und Degradation (14)
- 3 Gefahrgutumschließungen; Energiespeicher (8)
- 3.2 Gefahrguttanks und Unfallmechanik (8)
- 7.4 Baustofftechnologie (4)
- 8 Zerstörungsfreie Prüfung (3)
- 8.0 Abteilungsleitung und andere (2)
- 5.3 Polymere Verbundwerkstoffe (1)
- 7.2 Ingenieurbau (1)
- 8.2 Zerstörungsfreie Prüfmethoden für das Bauwesen (1)
- 9 Komponentensicherheit (1)
- 9.3 Schweißtechnische Fertigungsverfahren (1)
Eingeladener Vortrag
- nein (73)
Für Bauteile (Komponenten) von Versorgungsanlagen für flüssige Brenn- und Kraftstoffe muss die Beständigkeit der metallenen Werkstoffe und Polymere nachgewiesen werden. Im Anwendungsfall von Heizöl mit 20 % biogenen Anteilen in Form von Rapsölfettsäuremethylester (FAME, Biodiesel) ist es für eine konservative Beurteilung des Korrosionssystems Werkstoff/Medium/Umgebung wichtig, die Alterungseffekte des Mediums einzubeziehen.
Entwicklung eines Prüfverfahrens für die Untersuchung der Beständigkeit von metallenen Werkstoffen und Polymeren in Heizöl und Heizöl-FAME-Blends, das für eine Vorauswahl der Werkstoffe und zum Nachweis der Beständigkeit im Hinblick auf die bauaufsichtlichen Zulassungsverfahren geeignet ist.
Nachdem im Verbundprojekt COORAL das Hauptaugenmerk auf überkritisches CO2 gelegt wurde, d. h. Transport über kurze Strecken bei erhöhter Temperatur, wurde in CLUSTER ein größeres lokales Transport-Netzwerk betrachtet, bei dem CO2 bei geringeren Temperaturen, also vorwiegend im flüssigen Zustand transportiert wird. Wurden in COORAL die CO2-Ströme von Kohlekraftwerken untersucht, ging es in CLUSTER zusätzlich um die Emissionen von relevanten Industrien, deren CO2-Emissionen nicht ohne Weiteres vermieden werden können.
Aufgrund der Erfahrungen in COORAL konnte eine Auswahl von kommerziellen Werkstoffen getroffen werden, die für einen konkreten Einsatz für CCS zur Verfügung stünden. Die gemischten und fluktuierenden CO2-Zusammensetzungen sind bei geeigneten Begrenzungen der Begleit¬stoffe im CO2 bezüglich Korrosionsvorgänge beherrschbar. Die Machbarkeit eines lokalen CCS-Clusters erscheint daher gegeben, soweit dies die Anlagen für Kompression, Transport und Injektion betrifft.
Für Bauteile (Komponenten) von Versorgungsanlagen für flüssige Brenn- und Kraftstoffe muss die Beständigkeit der metallenen Werkstoffe und Polymere nachgewiesen werden. Im Anwendungsfall von Heizöl mit 20 % biogenen Anteilen in Form von Rapsölfettsäuremethylester (FAME, Biodiesel) ist es für eine konservative Beurteilung des Korrosionssystems Werkstoff/Medium/Umgebung wichtig, die Alterungseffekte des Mediums einzubeziehen.
Entwicklung eines Prüfverfahrens für die Untersuchung der Beständigkeit von metallenen Werkstoffen und Polymeren in Heizöl und Heizöl-FAME-Blends, das für eine Vorauswahl der Werkstoffe und zum Nachweis der Beständigkeit im Hinblick auf die bauaufsichtlichen Zulassungsverfahren geeignet ist. Ein Schwerpunkt wird bei den metallenen Werkstoffen auf der Erprobung von Messmethoden liegen, mit denen sich in kurzer Versuchszeit ein Korrosionsangriff detektieren lässt.
Die untersuchten Werkstoffe Aluminium, Stahl 1.0037, 1.4301, Kupfer, Messing (CuZn40Pb) und Zink (ZP0410) sind in B0, B20, B100 und in 6 Jahre altem B100 beständig.
Auch in einem Jahr alten B20 und in einem Jahr alten B100 sind die Werkstoffe beständig.
Bei Kupfer blieb die Korrosionsrate in der Flüssigphase sowohl in B20 (0 μ m/ a) als auch in B100 (4 μ m/ a) nach einem Jahr unverändert. Für das 6 Jahre alte B100 stieg die Korrosionsrate des Kupfers an (16 μ m/a). Im Gegensatz dazu sank bei Messing die Korrosionsrate in der Flüssigphase mit dem Alter des Brennstoffs, nach einem Jahr für B20 von 4 μ m/ a auf 1 μ m/a und für B100 von 36 μ m/ a auf 6 μ m/ a, im 6 Jahre alten B100 lag die Korrosionsrate des Messings bei 0 μ m/ a.
In 8 Jahre altem B10 trat bei Zink in der Flüssigphase Flächenkorrosion auf, es ist in dem Medium demnach nicht beständig. Messing zeigte örtliche Korrosion in der Gasphase, es ist folglich unbeständig und für den Einsatz in stark gealterten B10 nicht geeignet.
Aluminium, 1.0037, 1.4301 und Kupfer sind in dem 8 Jahre alten B10 beständig.
Die Änderung der Zugfestigkeit und der Reißdehnung von ACM, HNBR und FKM in Heizöl, B20 und gealterten B10 beträgt < 15 %. Diese Werkstoffe sind in Heizöl, B20 und in gealterten B10 unter Berücksichtigung des von der BAM zur Beurteilung der Beständigkeit festgelegten Grenzwertes von 15 % bei 40 °C als beständig zu bewerten.
PUR ist bei 40 °C nicht beständig in B20 und in gealtertem B10. Bei 70 °C ist HNBR nicht in B20 beständig aufgrund der Verringerung der Zugfestigkeit (40 %) und der Reißdehnung (50 %). FKM ist bei 70 °C in Heizöl und in B20 beständig.
The second edition of this textbook on physical electrochemistry, written by two experienced teachers of physical chemistry, corrosion engineering and materials science and engineering, covers the current knowledge which should be transferred to students of these fields.
In 20 chapters the fundamentals of electrochemistry, the most important electrochemical measurement techniques and applications of electrochemistry are covered.
It can be concluded that this study fulfills its intension of “serving as a key textbook in undergraduate courses” dealing with electrochemistry and being “a reference source for graduated students, researchers and engineers” interested in this field. Teachers will find sufficient content for preparing lectures on this topic. Even self‐learning is well supported by the clear structure, presented content and provided sources for further reading.
Dieser umfangreiche Leitfaden gibt Auskunft zur thermisch‐mechanischen Beständigkeit von 199 Eisen‐, 77 Nickelbasis‐ und 23 Kobaltbasislegierungen und ist ein sehr gutes und bestimmt erweiterbares Nachschlagewerk für Konstrukteure und Praktiker, die über den Einsatz geeigneter Werkstoffe in hohen Temperaturen entscheiden müssen.
Demonstrationsexperimente
(2019)
Korrosionsprüfung
(2019)
This study focuses on the corrosion mechanism of carbon steel exposed to an artificial geothermal brine influenced by carbon dioxide (CO2) gas. The tested brine simulates a geothermal source in Sibayak, Indonesia, containing 1500 mg/L of Cl-, 20 mg/L of SO4 2-, and 15 mg/L of HCO3-with pH 4. To reveal the temperature effect on the corrosion behavior of carbon steel, exposure and electrochemical tests were carried out at 70 °C and 150 °C. Surface analysis of corroded specimens showed localized corrosion at both temperatures, despite the formation of corrosion products on the surface. After 7 days at 150 °C, SEM images showed the formation of an adherent, dense, and crystalline FeCO3 layer. Whereas at 70 °C, the corrosion products consisted of chukanovite (Fe2(OH)2CO3) and siderite (FeCO3), which are less dense and less protective than that at 150 °C.
Control experiments under Ar-environment were used to investigate the corrosive effect of CO2. Free corrosion potential (Ecorr) and electrochemical impedance spectroscopy (EIS) confirm that at both temperatures, the corrosive effect of CO2 was more significant compared to that measured in the Ar-containing solution. In terms of temperature effect, carbon steel remained active at 70 °C, while at 150 °C, it became passive due to the FeCO3 formation. These results suggest that carbon steel is more susceptible to corrosion at the near ground surface of a geothermal well, whereas at a deeper well with a higher temperature, there is a possible risk of scaling (FeCO3 layer). A longer exposure test at 150 °C with a stagnant solution for 28 days, however, showed the unstable FeCO3 layer and therefore a deeper localized corrosion compared to that of seven-day exposed specimens.
Aufgrund der stark korrosiven Atmosphäre in Tunnelbauwerken kommt es aufgrund von Reinigungs- und Sanierungsmaßnahmen an Ein- und Anbauteilen aus nichtrostendem Stahl häufig zu wartungsbedingten Verkehrsbeeinflussungen und Tunnelsperrungen. Bislang ist nur eine kleine Gruppe rostfreier Edelstähle für die Verwendung in Tunnelbauwerken zugelassen. Im Sinne einer mittel- bis langfristigen Reduktion von Wartungsarbeiten besteht jedoch großes Interesse, die Einsatzmöglichkeiten alternativer nichtrostender Stähle zu erhöhen.
Um dies zu ermöglichen, entwickelten die Bundesanstalt für Materialforschung und -prüfung (BAM), gemeinsam mit dem Landesbetrieb Straßenbau NRW, in Zusammenarbeit mit der Informationsstelle Edelstahl Rostfrei (ISER), mit Unterstützung des Edelstahlherstellers Outokumpu und der Wilhelm Modersohn GmbH & Co. KG ein Forschungsprojekt zur Auslagerung von nichtrostenden Duplexstählen in Straßentunnel. Im Oktober 2019 beteiligte sich der Landesbetrieb Straßen, Brücken und Gewässer in Hamburg und ermöglichte die Auslagerung im Elbtunnel auszuweiten.
Der Vortrag behandelt die Grundlagen der Korrosion sowie einzelene Aspekte von Korrosionsschutzmethoden. Weiterhin werden Themen wie Bimetallkorrosion und Spaltkorrosion erläutert. Es werden passivierbare Werkstoffe und deren Eigenschaften im Hinblick auf einen korrosionsschutzgerechten Einsatz vorgestellt.
Der kritische, Korrosion auslösende Chloridgehalt für die Beurteilung der Korrosions-beständigkeit von Betonstahl in Geopolymerbetonen ist von großer Bedeutung für die Dauerhaftigkeitsprognose für bewehrte Elemente aus solchen Materialien. Es sind kaum experimentelle Daten in der Fachliteratur vorhanden und die vorliegenden Werte unterscheiden sich zwischen den Studien erheblich. In diesem Projekt wurde der kritische, Korrosion auslösende Chloridgehalt für Betonstahl (BSt 500) in flugaschebasierten (Ca-armen) Geopolymermörtel für verschiedene Beaufschlagungskombinationen bestimmt: Chloridbeaufschlagung mit 1 M NaCl-Lösung; Auslaugen in entionisiertem Wasser und anschließende Chloridbeaufschlagung im 1 M NaCl-Lösung; Auslaugen in entionisiertem Wasser, Carbonatisierung in Luft bei 20 °C und natürlicher CO2 Konzentration und anschließende Chloridbeaufschlagung mit 1 M NaCl-Lösung. Für Referenz-Zwecke wurde zusätzlich der Korrosion auslösende Chloridgehalt für eine Portland-Zement Mischung bei Auslagerung in 1 M NaCl-Lösung bestimmt.
Fireside Chat - Sharing PhD
(2019)
Since materials play an important role when designing and servicing industrial facilities. Also, for energy systems there is no way around. Selection of appropriate materials is an essential aspect for successful application and reliable service life. Future engineers must be made aware on the importance of this fact. So, they may prevail in techno‐economic discussions.
The book fulfills its intension of providing to students in science and engineering a comprehensive understanding of different energy processes and what role materials play in this conjunction. Also, it gives interested engineers and scientists an insight in this matter. After being introduced the user should dig deeper in the existing detailed knowledge available for materials selection within these special conditions to assure a reliable operation of the energy production facility.
Specific amounts of oxidizing and reductive impurities as well as some moisture were added to dense phase CO2 to replicate CO2 streams from sources in a CCS pipeline network. Due to the moisture content being only 50 ppmV no visible acid condensation took place. To simulate stress conditions at the inside pipeline surface due to fluid pressure (10 MPa) specimens were preloaded using a load frame. Experiments conducted at 278 K and at 313 K revealed the highest corrosion rate at lower temperature. Corrosive effect of impurities was strongest applying mixed atmosphere, containing oxidizing and reductive components, closely followed by CO2 streams with pure oxidizing character. By far, the lowest corrosion rate (10x lower) resulted from reductive atmosphere. In general, at constant temperature and pressure the CO2 stream composition strongly influences the morphology, thickness and composition of the corrosion products. Applying oxidizing or mixed impurities, iron hydroxides or oxides (e.g. goethite, hematite) occur as dominating corrosion products, capable to incorporate different amounts of sulfur. In contrast, using reductive atmosphere very thin corrosion layers with low crystallinity were developed, and phase identification by XRD was unfeasible. SEM/EDX analysis revealed the formation of Fe-O compounds, most likely attributed to the oxygen partial pressure in the system induced by CO2 (≥0.985 volume fraction) and volatile H2O. In addition to the surface covering corrosion layer, secondary phases had grown locally distributed on top of the layer. These compounds are characteristic for the applied atmosphere and vary in number, shape and chemical composition.
Für Anwender nichtrostender Stähle wird im neu überarbeiteten Merkbaltt 833 eine Planungshilfe für Anwendungen nichtrostender Stähle in Erdböden gegeben. Hinweise und Empfehlungen zur Werkstoffauswahl sowie allgemeine Hinweise zum Einsatz nichtrostender Stähle und auch Anwendungsbeispiele sind im neu überarbeitetn Merkblatt enthalten.
Ein neuer Ansatz bei elektrochemischen Korrosionsuntersuchungen kann durch den Einsatz von gelartigen Elektrolyten als Alternative zu wässrigen Prüfelektrolyten beschritten werden. Gelartige Elektrolyte ermöglichen minimalinvasive Untersuchungen an natürlich gebildeten Zinkdeckschichten. Dadurch können korrosionsrelevante Kennwerte ermittelt werden, die Aussagen zur Deckschichtbildung und zur Stabilität von atmosphärisch gebildeten Deckschichten erlauben. In diesem Beitrag wird anhand verschiedener Untersuchungen an Reinzink der Mehrwert von gelartigen Elektrolyten für die Korrosionsforschung und -prüfung verdeutlicht. Darüber hinaus werden neue Erkenntnisse zur Deckschichtbildung von Zink unter atmosphärischen Bedingungen vorgestellt.
Ein neuer Ansatz bei elektrochemischen Korrosionsuntersuchungen kann durch den Einsatz von gelartigen Elektrolyten als Alternative zu wässrigen Prüfelektrolyten beschritten werden. Gelartige Elektrolyte ermöglichen minimalinvasive Untersuchungen an natürlich gebildeten Zinkdeckschichten. Dadurch können korrosionsrelevante Kennwerte ermittelt werden, die Aussagen zur Deckschichtbildung und zur Stabilität von atmosphärisch gebildeten Deckschichten erlauben. In diesem Beitrag wird anhand verschiedener Untersuchungen an Reinzink der Mehrwert von gelartigen Elektrolyten für die Korrosionsforschung und -prüfung verdeutlicht. Darüber hinaus werden neue Erkenntnisse zur Deckschichtbildung von Zink unter atmosphärischen Bedingungen vorgestellt.
Der Vortrag verdeutlicht am Beispiel von Offshore-Windenergieanlagen, welchen Beitrag ein geeigneter Korrosionsschutz zu Fragen der Wirtschaftlichkeit, der Gesundheitstechnik und der Sicherheit leistet. Die Umweltverträglichkeit von Korrosionsschutzmaßnahmen wird anhand der Emission von chemischen Substanzen und Verbindungen beleuchtet.
In der aktuellen RL-SIB wie auch im Gelbdruck der Instandhaltungsrichtlinie ist bei Anwendung des Instandsetzungsprinzips W-Cl bzw. Verfahren 8.3 der Erfolg der Maßnahme durch Einbau und Messung von Korrosionsstrom-Mess-Einrichtungen nachzuweisen. Auch wird bei der Instandsetzung von chloridbelasteten Rissen bei Stahlbetonbauteilen durch Verpressen der Risse bzw. Aufbringen einer Rissbandage ein Korrosionsmonitoring empfohlen. Anerkannte Regelwerke oder Normen über Art und Aufbau des Monitoring-Systems sowie Kriterien zur Bewertung der Messergebnisse im Hinblick auf den Erfolg der Instandsetzungsmaßnahme gibt es derzeit nicht. Auch sind keine Untersuchungen zur Qualität der Messergebnisse veröffentlicht.
Ziel des Vorhabens ist die Ausarbeitung eines Regelwerks-Entwurfes für die Art und den Aufbau von Korrosionsmonitoring-Systemen sowie für Kriterien zur zuverlässigen Bewertung der Messergebnisse, mit denen der Erfolg bei verschiedenen Instandsetzungskonzepten überprüft werden kann.
Das Verhalten von Erdböden gegenüber metallenen Konstruktionswerkstoffen ähnelt in vielen Fällen der von neutralen Wässern. Der in natürlichen Erdböden vorhandene Wasseranteil bildet mit den löslichen Inhaltsstoffen eine Elektrolytlösung. Eine merkbare Korrosionsgeschwindigkeit tritt erst dann auf, wenn der Boden einen bestimmten Wassergehalt aufweist, der eine Sauerstoffdiffusion im Boden zur Oberfläche des Metalls gewährleistet. Von maßgebendem Einfluss auf die korrosionsverursachende Wirkung der Böden ist neben dem Feuchtegehalt, der die Leitfähigkeit des Bodens bestimmt, der pH-Wert. Verschiedene Bodenarten besitzen unterschiedliche Wasser- und Sauerstoffdurchlässigkeiten, sowie Unterschiede der gelösten Inhaltsstoffe wie Chloride oder Sulfate, wodurch sich das Korrosionsverhalten von Metallen in verschiedenen Böden stark unterscheidet. In der DIN 50929-3 werden Böden in vier verschiedene Bodenklassen mit Korrosionsbelastungen von sehr niedrig bis hoch unterteilt. Durch verschiedene Bodenanalysen und örtliche Gegebenheiten kann nach DIN 50929-3 zwar die Korrosivität eines Bodens bestimmt werden, jedoch ist die Reproduzierbarkeit eines Bodens (Prüfmediums) praktisch nicht möglich.
Es gibt jedoch Überlegungen, wie die Einstellung einer Bodenklasse durch Verwendung von Normsand und der Zugabe von Stoffen erzielt werden kann, wodurch die Reproduzierbarkeit eines Bodens ermöglicht wird.
Messing unter Druck
(2019)
Dictionary of Metallurgy and Metal Processing - English-German – German-English (Book review)
(2019)
The first issue of this classic dictionary contains highly specialized terms, not only of the area of metallurgy but also of welding, soldering and corrosion. Special attention was paid by the author to a correct reference of each term according to the field of application.
Finally, this book fulfills the intension of its author, to collect relevant terms with the correct pendant from a huge variety of sources and applications. It provides the user a foundation for correct terminology and communication for international contacts.
Biodiesel is subject to degradation processes like oil and grease. The oxidative degradation products of vegetable oil esters in biodiesel particularly lead to enhanced sedimentation in blended fuels.
The polarity of biodiesel increases its solvency and facilitates permeation and extraction. Solvation, swelling and/or extraction lead to changes in the physical properties and chemical changes of polymeric materials. It also accelerates the degradation (hydrolysis and oxidation) of these materials with the loss of additives and stabilizers.
The objective of this research was to determine the resistance of frequently used polymeric materials such as ACM, EPDM, FKM, FVMQ, CR, CSM, IIR, HNBR, NBR, PA, PE; POM, PUR, PVC and VMQ in biodiesel and heating oil with 10 %/20 % biodiesel (B10/B20) at 40°C and 70°C.
Mass, tensile strength and breaking elongation of the test specimens were determined before and after the exposure for 84 days in the biodiesel heating oil blends. The visual examination of some elastomer test specimens clearly showed the great volume increase until break or partial dissolution. Shore hardness A and D were determined before and after exposure of the test specimens in the biofuels for 42 days.
The elastomers CR, CSM, EPDM, IIR, NBR and VMQ were generally not resistant to biodiesel and B10 at 40°C and 70°C. FKM, ACM, HNBR, PA, PE, POM, and PVC showed high compatibility in B10/B20 at 40°C. A lower compatibility was determined for ACM in biodiesel. ACM and HNBR were not resistant in B20 at 70°C.
Effizienz und Qualität sind schon immer Antriebsmotoren für die Wirtschaft. Um das heutzutage in einer stetig schneller agierenden Welt zu erreichen, wird konsequentes Prozessmanagement immer wichtiger. Dabei werden Prozesse nicht nur klar und eindeutig beschrieben, sondern auch Kompetenzen, Aufgaben und Verantwortlichkeiten festgelegt, um das Resultat für den Kunden in den Fokus zu rücken und zeitraubende Hierarchiekämpfe zu vermeiden.
Der Autor untermalt die gut strukturierten Textpassagen, in denen wichtige Schlagworte fett abgedruckt sind, mit vielen Schaubildern zu Prozessen und übersichtlichen Tabellen. Er gibt dem Leser Werkzeuge in Form von Checklisten sowie Diagnoseplänen und Analyseformularen.
Gleichzeitig wird durch beispielhaft ausgefüllte Formulare (Checklisten) der Praxisbezug anhand unterschiedlicher Branchenbereiche wie z.B. Controlling, Produktion, Medizin, etc. hergestellt. Somit liegt hier ein Arbeitsbuch vor für jeden, der gleich losstarten möchte.
This contribution provides current findings regarding materials susceptibility for carbon capture, utilization and storage (CCUS) applications. Basing on results gathered in 2 German long-term projects (COORAL and CLUSTER) suitable materials are introduced as well as dominating impurities of the CO2-stream and corrosion mechanisms. Investigations cover the whole CCUS process chain and provide material recommendations for certain parts.
This contribution provides current findings regarding materials susceptibility for carbon capture, utilization and storage (CCUS) applications. Basing on results gathered in 2 German long-term projects (COORAL and CLUSTER) suitable materials are introduced as well as dominating impurities of the CO2-stream and corrosion mechanisms. Investigations cover the whole CCUS process chain and provide material recommendations for certain parts.
Susceptibility of 304 stainless steel to crevice corrosion in electrochemically active fluids
(2019)
The susceptibility of AISI 304 stainless steel to crevice corrosion on the effect of contact with electrochemically active fluids was investigated using exposure and stepwise potentiostatic polarisation. Crevice materials made up of 304 SS and Polyether ether ketone (PEEK) forming two kinds of crevices including 304 SS-to-PEEK and 304 SS-to-304 SS were tested.
Susceptibility of 304 stainless steel to crevice corrosion in electrochemically active fluids
(2019)
The susceptibility of AISI 304 stainless steel to crevice corrosion on the effect of contact with electrochemically active fluids was investigated using exposure and stepwise potentiostatic polarisation. Crevice materials made up of 304 SS and Polyether ether ketone (PEEK) forming two kinds of crevices including 304 SS-to-PEEK and 304 SS-to-304 SS were tested.
Susceptibility of 304 stainless steel to crevice corrosion in electrochemically active fluids
(2019)
The susceptibility of AISI 304 stainless steel to crevice corrosion on the effect of contact with electrochemically active fluids was investigated using exposure and stepwise potentiostatic polarisation. Crevice materials made up of 304 SS and Polyether ether ketone (PEEK) forming two kinds of crevices including 304 SS-to-PEEK and 304 SS-to-304 SS were tested.
Ziel des Projektes ist die Qualifizierung von Duplexstählen in Tunnelbauwerken um die Einsatzmöglichkeiten alternativer nichtrostender Stähle zu den bislang gebräuchlichen rostfreien Edelstählen 1.4404 und 1.4571 zu eruieren. Da Duplexstähle im Vergleich zu austenitischen Stählen über eine doppelt so hohe Festigkeit verfügen, können Bauteile schlanker konstruiert werden, wodurch Material eingespart werden kann. Neben der Wirtschaftlichkeit muss die Dauerhaftigkeit untersucht werden. Dazu wurden speziell konzipierte Wand- und Deckenracks mit unterschiedlichen metallenen Werkstoffen und Oberflächen hergestellt und in den Tunnelbauwerken montiert. Nach bestimmten Auslagerungszeiten von bis zu drei Jahren werden die Proben demontiert und auf ihr Korrosionsverhalten untersucht. Ein weiteres Ziel neben der Qualifizierung der Werkstoffgruppe sind die Reduktion der Instandsetzungs- und Wartungsmaßnahmen der Tunnelbetreiber
Aus Rapsöl gewonnener Biodiesel ist eine umweltfreundliche Alternative zu fossilen Energiequellen. In der Europäischen Union, in der 80 % der ölhaltigen Brennstoffe importiert werden müssen, besteht zudem ein Interesse, die Abhängigkeit von exter-nen Ölversorgern zu reduzieren.
Bei jeder Veränderung der Zusammensetzung eines Brennstoffs muss auch die Ma-terialverträglichkeit gewährleistet bleiben. Es stellt sich die Frage, ob Elastomere im Vergleich zu reinem Heizöl auch in Heizöl mit 20 % Biodiesel (B20) beständig sind.
Die Polarität des Biodiesels erhöht die Quellung und fördert die Permeation und Ex-traktion. Sowohl Quellung als auch Extraktion bedingen Änderungen der physikali-schen Eigenschaften der Elastomere. Extraktion verändert die chemische des Heiz-öls. Diese chemischen Veränderungen können auch den Abbau (Hydrolyse und Oxi-dation) der Polymere durch das Herauslösen von Additiven und Stabilisatoren be-schleunigen.
Ziel dieser Arbeit war die Bestimmung der Beständigkeit der Elastomere ACM (Poly-acrylatkautschuk), HNBR (Hydrierter Acrylnitrilbutadienkautschuk), FKM (Fluorkaut-schuk) und PUR (Polyurethan) in Heizöl und im Heizölgemisch B20.
Prüfkörper der Elastomere wurden für 42 Tage (Härteprüfung) und 84 Tage (Zugprü-fung) bei 40 °C ausgelagert. Anschließend wurde die Änderung der Masse, Shore Härte A, Zugfestigkeit, und Reißdehnung bezogen auf die Werte vor der Aus-lagerung bestimmt. Die weniger zur Quellung neigenden Elastomere FKM und HNBR wurden zusätzlich bei 70 °C ausgelagert.
Um die Elastomere im verpressten Zustand zu testen, wurde der Druckverformungs-rest nach DIN ISO 815 bestimmt. Hierzu wurden zylindrische Prüfkörper aus ACM, HNBR und FKM verpresst und in Heizöl und Heizöl mit 20 % FAME für 3, 7, 14, 28, 56 und 90 Tage bei 40 °C ausgelagert. Anschließend wurde über die Dickenmes-sung der Druckverformungsrest ermittelt. Zum Vergleich wurden Prüfkörper verpresst und ohne Medium bei 40 °C ausgelagert.
In den internationalen Normen wurde kein Grenzwert für die Veränderung der Zugei-genschaften und der Härte für eine positive Bewertung der Beständigkeit festgelegt. Deshalb wurde in der BAM ein Grenzwert von 15 % für die Beständigkeitsbewertung herangezogen.
Bei 40 °C lag die Änderung der Zugeigenschaften und der Shore Härte von ACM, HNBR und FKM in Heizöl und in B20 unter 15 %. Folglich sind ACM, HNBR und FKM bei 40 °C in Heizöl und in B20 beständig. PUR ist bei 40 °C in Heizöl beständig, je-doch nicht für eine Verwendung in B20 geeignet, da sich die Zugfestigkeit und Reiß-dehnung um 50 % vermindert haben.
Bei 70 °C ist FKM in Heizöl und B20 beständig, wohingegen HNBR an seine Einsatz-grenzen gelangt und unbeständig ist, in B20 haben sich die Zugfestigkeit um 40 % und die Reißdehnung um 50 % reduziert.
In Europe biodiesel gained from rapeseeds are considered as an alternative to common fossil fuels due to its environmental performance and its independence from import of raw materials. Biodiesel is also suitable to serve as blending component to heating oil. In that case, it must be considered that changes of fuel composition might cause material degradation.
The objective of this research was to investigate the resistance of metallic materials exposed to heating oil, heating oil blend B20 with 20 % biodiesel and pure biodiesel. Furthermore, the resistance of metals to eight-year aged B10 and six-year aged pure biodiesel was evaluated. Ageing of biodiesel forms acids and water which might propagate metal corrosion. The investigated metals (aluminium, unalloyed steel, austenitic CrNi-steel, copper, die cast zinc and brass) are commonly used for components in middle distillate facilities.
According to DIN 50905-4 the immersed metals were exposed in a climate chamber at 50°C for 4 weeks. The metallic materials were evaluated as resistant if the annual corrosion rate due to uniform corrosion remained under 0.1 mm/year and no localized corrosion in the form of pitting occurred.
The corrosion rates of the exposed materials stayed far below the limit of 0.1 mm/year for all tested fuels. An exception was die cast zinc ZP0410 in eight-year aged B10; a corrosion rate up to 0.3 mm/year due to uniform corrosion was measured. In no case localized corrosion occurred. Copper and brass caused discolouration of biodiesel from yellow to green.
In conclusion, the tested metallic materials were resistant in heating oil, heating oil blend B20 and pure biodiesel at 50 °C. Even the metals exposed to six-year aged biodiesel and eight-year aged B10 showed no uniform or localized corrosion; except for zinc, which was not resistant in eight-year aged B10.
Zinc materials are of high importance in the field of corrosion protection. For example, almost half of the annual production of zinc is used as anti-corrosive layer for steel components, particularly under atmospheric conditions. The corrosion protection is frequently ascribed to zinc carbonate species with low solubility which form on the metal surface under atmospheric conditions. Due to the technological importance and wide use of zinc materials, its corrosion behavior and the formation of reaction products has been intensively investigated over decades.
Assuming atmospheric corrosion conditions, an initial native passive film of few nanometers thickness forms spontaneously. It consists of zinc oxide and hydroxide, transforming into various species in dependence of the surrounding atmospheric conditions.
This study focusses on the investigation of corrosion product layers on massive titanium-zinc sheets, formed during short- and mid-term exposure experiments by Fourier-transformed infrared spectroscopy. This method enables the investigation of extremely thin native passive films which form during the initial hours of exposure. Furthermore, aged surface layers are analyzed which were formed by transformation of initial passive layers over the time of several weeks. The spectroscopic investigations are complemented by scanning electron microscopy (SEM/EDX) in order to obtain information on the chemical composition and morphology of the corrosion products. The combination of both methods offers a comprehensive view on the processes occurring in the early stages of zinc corrosion.
Carbon Capture and Storage (CCS) is identified as an excellent technology to reach the target of CO2 reduction. However, the safety issue and cost-effectiveness hinder the future of CCS. For the reliability and safety issues of injection wells, the corrosion resistance of the materials used needs to be determined.
In this study, representative low-cost materials including carbon steel 1.8977 and low alloyed steel 1.7225 were investigated in simulated pore water at 333 K and under CO2 saturation condition to represent the worst-case scenario: CO2 diffusion and aquifer fluid penetration. These simulated pore waters were made from relevant cement powder to mimic the realistic casing-cement interface. Electrochemical studies were carried out using the pore water made of cement powder dissolved in water in comparison with those dissolved in synthetic aquifer fluid, to reveal the effect of cement as well as formation water on the steel performance. Two commercially available types of cement were investigated: Dyckerhoff Variodur® and Wollastonite. Variodur® is a cement containing high performance binder with ultra-fine blast furnace slag which can be used to produce high acid resistance concrete. On the other hand, Wollastonite is an emerging natural material mainly made of CaSiO3 which can be hardened by converting to CaCO3 during CO2 injection.
The results showed the pH-reducing effect of CO2 on the simulated pore water/aquifer (from more than 10 to less than 5) leading to the active corrosion process that happened on both 1.8977 and 1.7225. Electrochemical characterization showed negative free corrosion potential and polarisation curves without passive behaviors. The tested coupons suffered from pitting corrosion, which was confirmed by surface analysis. Interestingly, basing on the pit depth measurements from the tested coupons and the hardness of cement powder, it is suggested that Variodur® performed better than Wollastonite in both aspects. The electrochemical data was compared to that resulted from exposure tests to give a recommendation on material selection for bore-hole construction.
Der Einsatz von Edelstahl Rostfrei in Böden wird nur in wenigen Regelwerken behandelt, somit müssen sich Anwender und mPlaner auf Erfahruzngen und Studien stützen um Hilfestellung zum Beispiel zur Werkstoffauswahl zu erhalten. Der Vortrag stellt das von der BAM und der ISEr überarbeiteet Merkblatt 833 vor, welches den Einsatz von Edelstahl Rostfrei im Erdboden bahandelt.
Carbon Capture and Storage (CCS) is identified as an excellent technology to reach the target of CO2 reduction. However, the safety issue and cost-effectiveness hinder the future of CCS. For the reliability and safety issues of injection wells, the corrosion resistance of the materials used needs to be determined.
In this study, representative low-cost materials including carbon steel 1.8977 and low alloyed steel 1.7225 were investigated in simulated pore water at 333 K and under CO2 saturation condition to represent the worst-case scenario: CO2 diffusion and aquifer fluid penetration. These simulated pore waters were made from relevant cement powder to mimic the realistic casing-cement interface. Electrochemical studies were carried out using the pore water made of cement powder dissolved in water in comparison with those dissolved in synthetic aquifer fluid, to reveal the effect of cement as well as formation water on the steel performance. Two commercially available types of cement were investigated: Dyckerhoff Variodur® and Wollastonite. Variodur® is a cement containing high performance binder with ultra-fine blast furnace slag which can be used to produce high acid resistance concrete. On the other hand, Wollastonite is an emerging natural material mainly made of CaSiO3 which can be hardened by converting to CaCO3 during CO2 injection.
The results showed the pH-reducing effect of CO2 on the simulated pore water/aquifer (from more than 10 to less than 5) leading to the active corrosion process that happened on both 1.8977 and 1.7225. Electrochemical characterization showed negative free corrosion potential and polarisation curves without passive behaviors. The tested coupons suffered from pitting corrosion, which was confirmed by surface analysis. Interestingly, basing on the pit depth measurements from the tested coupons and the hardness of cement powder, it is suggested that Variodur® performed better than Wollastonite in both aspects. The electrochemical data was compared to that resulted from exposure tests to give a recommendation on material selection for bore-hole construction.
Geothermal energy is one of the most promising energy resources to replace fossil fuel. To extract this energy, hot fluids of various salts and gases are pumped up from a geothermal well having a certain depth and location. Geothermal wells in volcanic regions often contain highly corrosive CO2 and H2S gases that can be corrosive to the geothermal power-plants, which are commonly constructed of different steels, such as carbon steel. This research focuses on the corrosion behaviour of carbon steel exposed to an artificial geothermal fluid containing CO2 gas, using an artificial acidic-saline geothermal brine as found in Sibayak, Indonesia. This medium has a pH of 4 and a chloride content of 1,500 mg/L. Exposure tests were conducted for seven days at 70 °C and 150 °C to simulate the operating temperatures for low and medium enthalpy geothermal sources. Surface morphology and cross-section of the specimens from the above experiments were analysed using scanning electron microscope (SEM) and energy dispersive X-ray (EDX). Electrochemical tests via open circuit potential (OCP) and electrochemical impedance spectroscopy (EIS) were performed to understand the corrosion processes of carbon steel in CO2-containing solution both at 70 °C and 150 °C. Localized corrosion was observed to a greater extent at 70 °C due to the less protectiveness of corrosion product layer compared to that at 150 °C, where FeCO3 has a high corrosion resistance. However, a longer exposure test for 28 days revealed the occurrence of localized corrosion with deeper pits compared to the seven-day exposed carbon steel. In addition, corrosion product transformation was observed after 28 days, indicating that more Ca2+ cations incorporate into the FeCO3 structure.
Der Vortrag stellt das WIPANO-Vorhaben GELELEK vor. Zu Beginn wird die Problemstellung und Projektidee kurz erläutert. Anschließend wird ein Überblick über die Projektpartner, Projektziele und Arbeitsschritte gegeben, sowie die ausgewählten Probenbleche vorgestellt. Abschließend wurde noch eine Einladung zur Teilnahme am projektbegleitenden Ausschuss ausgesprochen.
Der Vortrag stellt ein neuartiges Korrosionsprüfverfahren für Zinküberzüge auf Basis gelartiger Elektrolyte vor und führt die Vorteile gegenüber konventionellen Prüfverfahren auf. Basierend auf den Ergebnissen wird die Idee für einen IGF-Projektantrag in Kooperation mit dem Fraunhofer IKTS vorgestellt.
Biodiesel is viewed as a major source of energy. In areas such as the European Union, where 80 % of the oil-based fuel is imported, there is also the desire to reduce dependence on external oil supplies.
Materials compatibility is a major concern whenever the fuel composition is changed. The question arises of whether polymeric materials are resistant to heating oil with 20 % biodiesel (B20) in comparison to pure heating oil.
The polarity of biodiesel increases its solvency and facilitates permeation and extraction. Solvation, swelling and/or extraction lead to changes in the physical properties. Extraction alters the fuel chemistry. These chemical changes could also accelerate the degradation (hydrolysis and oxidation) of the polymeric material with the loss of additives and stabilizers.
The objective of this research was to determine the resistance of frequently used materials for components in middle distillate facilities such as ACM, FKM, HNBR, PA, PE, POM, PUR and PVC in heating oil and heating oil blend B20 for 84 days at 40 °C, and FKM, HNBR, PA, POM, PUR and PVC at 70 °C.
Mass, tensile strength, breaking elongation and Shore hardness A (D) of the test specimens were determined before and after exposure for 84 (42) days in the test fuels under static conditions.
For the investigations under compressed conditions, the mass and the compression set of FKM test specimens were determined before and after exposure for 3, 7, 14, 28, 56 and 90 days in B20 at 40 °C and 70 °C according to ISO 815-1 “Rubber, vul-canized or thermoplastic - determination of compression set – Part 1: At ambient or elevated temperatures”.
There is not determined a threshold for the reduction in tensile properties and Shore hardness in the international standards. Therefore, a threshold of 15 % was determined for the evaluation of the compatibility.
The change of tensile strength and breaking elongation of test specimens made of ACM, FKM, HNBR, PA, PE, POM, PUR and PVC exposed to heating oil and the blend B20 was less than 15 % at 40 °C. A maximum reduction in Shore hardness A of 14 % was determined for ACM at 40 °C and for HNBR of 15 % at 70 °C.
It can be concluded that ACM, FKM, HNBR, PA, PE, POM, PVC and PUR were resistant in B20 at 40°C. FKM, PA, POM and PVC were evaluated as resistant in heat-ing oil and B20 at 70 °C, HNBR and PUR were not resistant in these fuels at 70°C.
Based on the mass increase and compression set values of FKM test specimens it can be stated that FKM is resistant in B20 under compressed conditions at 40 °C and 70 °C.
Zum Schutz vor Korrosionsprozessen werden metallene Werkstoffe in der Automobilindustrie üblicherweise mit komplexen Beschichtungssystemen versehen. Durch eine Beschädigung des Beschichtungssystems kann bei Zutritt von Feuchtigkeit und korrosionsstimulierenden Ionen das Metallsubstrat korrodieren und unter Umständen die Beschichtung im Bereich neben der Verletzung enthaften. Dabei gibt es verschiedene Mechanismen, die zu einer Unterwanderung und Enthaftung der Beschichtung führen können. In jedem Fall wird aber die Dauerhaftigkeit des Korrosionsschutzes negativ beeinflusst und die Lebensdauer des Bauteils herabgesetzt.
Die Industrie versucht deshalb, Beschichtungssysteme zu entwickeln, die dem Vorgang der kathodischen Enthaftung bestmöglich widerstehen können. Einen kritischen Entwicklungs- und Qualifizierungsschritt stellt dabei die geeignete Prüfung auf kathodische Unterwanderung und Enthaftung dar, da eine Prüfung der Beschichtung möglichst schnell und kosteneffizient zu belastbaren Ergebnissen führen soll. Neben den industriell üblichen Salzsprühnebeltests kommen häufig elektrochemische Polarisationstests zur Anwendung. Verschiedene Automobilherstellerhaben verwenden jeweils angepasste Tests, die sich bezüglich der Prüfparameter unterscheiden. Bei allen Testvarianten wird aber versucht, durch Verschärfung der Prüfparameter kurze Prüfzeiträume zu erreichen. Dabei kann es aber dazu kommen, dass die real ablaufenden Mechanismen der Unterwanderung beeinflusst und verändert werden und das Prüfergebnis von Ergebnissen im Feld zum Teil stark abweicht.
Im Vortrag werden mit Blick auf die geltenden Regelwerke und Normen die Unterschiede verschiedener Prüfmethoden zur kathodischen Enthaftung bei organischen Beschichtungen vorgestellt und deren Aussagekraft kritisch betrachtet. Am Beispiel von systematischen Versuchsreihen an einem ausgewählten Kurzzeittest werden die Grenzen einiger Methoden herausgearbeitet und die Anwendbarkeit für Qualitätsprüfungen betrachtet. Durch den Ansatz der statistischen Versuchsplanung wird der Einfluss einzelner Prüfparameter auf die Enthaftung und das Ergebnis des Kurzzeittests gezeigt.
Investigation of the salinization in marine and offshore environment - test methods and challenges
(2019)
Salinization and contamination of metal surfaces by chloride-containing aerosols is of great importance with regard to corrosion phenomena in the maritime sector and in offshore applications. Especially Offshore Wind Turbines are exposed to extreme corrosive conditions due to high chloride concentrations in the atmosphere and the resulting high chloride deposition rates. It is of great importance to evaluate to what extent salinization of the surface influences the corrosion protection of coatings and pitting occurrence on stainless steels under atmospheric conditions to evaluate the durability of metallic building structures in offshore and marine environments. The evaluation of the scientific literature and regulatory guidelines has shown that there are still many open questions regarding the contamination of metal surfaces by chlorides. This contribution will discuss how salinization of metal surfaces is evaluated and monitored according to current standards and guidelines. Future challenges concerning test methods and the application of evaluated salinization values and deposition rates will be discussed.
Rezension: Wörterbuch der Metallurgie und Metallverarbeitung ‐ Englisch‐Deutsch – Deutsch‐Englisch
(2019)
Die erste Auflage dieses klassischen Wörterbuches enthält hochspezialisierte Fachbegriffe nicht nur aus dem Bereich der Metallurgie, sondern auch zum Schweißen, Löten und zur Korrosion. Besonderer Wert wurde vom Autor auf einen korrekten Bezug zum jeweiligen Anwendungsgebiet gelegt.
Letztendlich erfüllt das Wörterbuch das Ansinnen seines Autors,aus der Vielzahl von Quellen und Anwendungsgebieten die relevanten Begriffe mit dem korrekten Pendant zusammenzustellen und bietet dem Nutzer eine Grundlage für korrekte Begrifflichkeit und Kommunikation im internationalen Kontakt.
Das in der 3. Auflage vorliegende Fachbuch wird die praktische Arbeit des Ingenieurs bei der Beurteilung von Verschleißerscheinungen unterstützen. In acht Kapiteln behandeln die Autoren alle interessanten Aspekte zu diesem Thema.
Zielgruppen sind Maschinen-bauingenieure, Techniker und Werkstofftechniker in der Entwicklung, Konstruktion und Instandhaltung. Sie werden für ihre Arbeit im Buch gute Unterstützung und Anregungen für ihre praktische Arbeitfinden.
In this also completely rewritten and reorganized second part of the two‐volume set 45 international experts comprise the current knowledge of conjugated polymers. In addition to part one on properties, processing characterization and morphology, 16 chapters cover perspectives, theory and new materials.
Finally, it can be concluded that this 4th edition of this handbook fulfills, like the first part, its intention, to be the definitive resource on the topic of conducting polymers. This is assured by the updated and added contributions of all authors, which consider the significant developments both in fundamental understanding, progress and applications since publication of the previous edition. So, it can be recommended to everyone, who wants to get a comprehensive overview on conjugated polymers, not just to researchers, advanced students, and industry professionals working in materials science and engineering.
The corrosion of steel in reinforced concrete structures is one of the main threats to their durability. Based on the scientific achievements of the past decades the knowledge about the deterioration mechanisms and possible repair strategies for corrosion induced damages have found their way into practice.
It is common sense, that a detailed assessment of the structure is the foundation for a successful repair measure. In addition to the “traditional” singular on-site-procedures such as measurement of concrete cover, carbonation depth, half-cell potentials and chloride contents the monitoring of corrosion related parameters has gained in importance over the past few years.
The advantages of a corrosion monitoring are obvious. In new buildings, structural elements which cannot be assessed after completion (e.g. tunnel segments), or members with electrically isolating coatings can be monitored by means of integrated sensors providing an insight into the development of crucial parameters such as electrochemical potentials, corrosion currents and the electrical resistivity of the concrete. A less known but very beneficial field of application is the use of corrosion monitoring as an integral part of a repair measure based on principles such as the cathodic protection of steel in concrete (CP) or increasing the electrical resistivity of the concrete (IR). By implementing a corrosion monitoring system, it is possible to survey the time dependent effect of the repair measure on the corrosion process which may lead to a confirmation of successful repair measure or to a modification of the repair strategy.
As the principle of cathodic protection for steel in concrete is a recognized repair measure today, the number of applications increases steadily and thus increasing the relevance for corrosion monitoring. Nevertheless, no standards or guidelines concerning the corrosion monitoring are available in Germany today, making it difficult to implement corrosion monitoring in common practice.
With this in mind an international task group formed to develop the specification B12 “Corrosion Monitoring of Reinforced and Prestressed Concrete Structures” published by the German Society for Non-Destructive Testing, DGZfP, spring 2018.
This paper will present the new specification B12 by highlighting the basic measurement principles and illustrating the potentials of corrosion monitoring for new and existing concrete structures by means of case studies.
This work presents machine learning-inspired data fusion approaches to improve the non-destructive testing of reinforced concrete. The principal effects that are used for data fusion are shown theoretically. Their effectiveness is tested in case studies carried out on largescale concrete specimens with built-in chloride-induced rebar corrosion. The dataset consists of half-cell potential mapping, Wenner resistivity, microwave moisture and ground penetrating radar measurements. Data fusion is based on the logistic Regression algorithm.
It learns an optimal linear decision boundary from multivariate labeled training data, to separate intact and defect areas. The training data are generated in an experiment that simulates the entire life cycle of chloride-exposed concrete building parts. The unique possibility to monitor the deterioration, and targeted corrosion initiation, allows data labeling.
The results exhibit an improved sensitivity of the data fusion with logistic regression compared to the best individual method half-cell potential.
The corrosion of steel in reinforced concrete structures is one of the main threats to their durability. Based on the scientific achievements of the past decades the knowledge about the deterioration mechanisms and possible repair strategies for corrosion induced damages have found their way into practice.
It is common sense, that a detailed assessment of the structure is the foundation for a successful repair measure. In addition to the “traditional” singular on-site-procedures such as measurement of concrete cover, carbonation depth, half-cell potentials and chloride contents the monitoring of corrosion related parameters has gained in importance over the past few years.
The advantages of a corrosion monitoring are obvious. In new buildings, structural elements which cannot be assessed after completion (e.g. tunnel segments), or members with electrically isolating coatings can be monitored by means of integrated sensors providing an insight into the development of crucial parameters such as electrochemical potentials, corrosion currents and the electrical resistivity of the concrete. A less known but very beneficial field of application is the use of corrosion monitoring as an integral part of a repair measure based on principles such as the cathodic protection of steel in concrete (CP) or increasing the electrical resistivity of the concrete (IR). By implementing a corrosion monitoring system, it is possible to survey the time dependent effect of the repair measure on the corrosion process which may lead to a confirmation of successful repair measure or to a modification of the repair strategy.
As the principle of cathodic protection for steel in concrete is a recognized repair measure today, the number of applications increases steadily and thus increasing the relevance for corrosion monitoring. Nevertheless, no standards or guidelines concerning the corrosion monitoring are available in Germany today, making it difficult to implement corrosion monitoring in common practice.
With this in mind an international task group formed to develop the specification B12 “Corrosion Monitoring of Reinforced and Prestressed Concrete Structures” published by the German Society for Non-Destructive Testing, DGZfP, spring 2018.
This paper will present the new specification B12 by highlighting the basic measurement principles and illustrating the potentials of corrosion monitoring for new and existing concrete structures by means of case studies.
An important aspect with regard to the service life of zinc based galvanic anodes and the durability of the corrosion protection of steel in concrete is the “galvanic chloride extraction”. Chloride ions move in the electric field generated by the current, flowing between the galvanic anode and the cathodic steel. Migration leads to an accumulation of anions, e.g. chloride ions, at the anode and depletion of chlorides near the steel rebar surface. The ion migration was studied on steel reinforced concrete specimens admixed with 3 wt.% chloride/wt. cement and galvanically protected by a surface applied embedded zinc anode (EZA). The zinc anode was embedded and glued to the concrete surface by a geo-polymer based chloride free binder. The EZA was operated over a period of 1 year and the ion distribution between anode (EZA) and cathode (steel reinforcement) was studied by laser induced breakdown spectroscopy (LIBS) after 5 months, 7 months and 12 months. The results show that chloride ions efficiently migrate in the direction of the zinc-anode and accumulate there. Chloride distribution in the EZA correlates with the distribution of zinc ions generated by the anodic dissolution of the zinc anode in the binder matrix. The microstructure of the binder matrix and its interface to the zinc-anode are studied by REM/EDX – preliminary results will be reported.
Investigation of the salinization in marine and offshore environment - test methods and challenges
(2019)
Salinization and contamination of metal surfaces by chloride-containing aerosols is of great importance with regard to corrosion phenomena in the maritime sector and in offshore applications. Especially Offshore Wind Turbines are exposed to extreme corrosive conditions due to high chloride concentrations in the atmosphere and the resulting high chloride deposition rates. It is of great importance to evaluate to what extent salinization of the surface influences the corrosion protection of coatings and pitting occurrence on stainless steels under atmospheric conditions to evaluate the durability of metallic building structures in offshore and marine environments. The evaluation of the scientific literature and regulatory guidelines has shown that there are still many open questions regarding the contamination of metal surfaces by chlorides. This contribution will discuss how salinization of metal surfaces is evaluated and monitored according to current standards and guidelines. Future challenges concerning test methods and the application of evaluated salinization values and deposition rates will be discussed.
Electrochemical deposition of polyaniline on carbon steel for corrosion study in geothermal solution
(2019)
Polyaniline has been widely developed for many applications, e.g. sensor, supercapacitor components, electrochromic devices, and anticorrosion pigments. Although the addition of polyaniline pigment in organic coatings has been an alternative for corrosion protection in industrial applications, the protection mechanism is still not fully understood. Herein in this study, as a part of the development of polyaniline/silicon dioxide coating for geothermal application, polyaniline has been deposited electrochemically on carbon steel surface in oxalic acid medium and tested in geothermal solution to understand the contribution of polyaniline to the corrosion protection of a polyaniline-based composite in the geothermal system. To observe the surface/interface reaction between the electrolyte and electrode surface during the electrochemical polymerization, electrochemical impedance spectroscopy (EIS) was applied after each cycle. For corrosion study in the geothermal application, an artificial geothermal solution was used with the composition of 1,500 mg/l Cl⁻, 20 mg/l SO₄²⁻, 15 mg/l HCO₃⁻, 200 mg/l Ca²⁺, 250 mg/l K⁺, and 600 mg/l Na⁺, and pH 4 to simulate a geothermal brine found in Sibayak, Indonesia. An electrochemical measurement was performed by monitoring the open circuit potential over seven days, with the interruption by EIS every 22 hours. The experiments were performed at room temperature and 150 °C (1 MPa) in an oxygen-free environment. Impedance spectra showed a reduction of the total impedance value of approximately 10 times for specimens measured at 150 °C compared to the specimens measured at room temperature, suggesting a less stable layer at high temperature.
Geothermal energy is an interesting alternative to polluting fossil energy sources. Therefore, in Belgium, two wells have been drilled for a deep geothermal power plant. However, the environment to which the installations are exposed is challenging. The geothermal brine has 165 g/l total dissolved solids (of which 90% are sodium and chlorine) and the production temperature can be up to 130 °C. To assess their suitability to be used in a geothermal power plant, the corrosivity of the artificial brine to three common construction materials was investigated with exposure and electrochemical tests. The metals under consideration are a low-alloyed carbon steel (S235JR), an austenitic stainless steel (UNS S31603) and a duplex stainless steel (UNS S31803). The carbon steel, that was found to corrode uniformly, could be considered as a constructional material if a sufficient wall thickness is chosen. The austenitic stainless steel and the duplex stainless steel demonstrate very low uniform
corrosion rates. They are however susceptible to pitting and crevice corrosion. To guarantee safe operation of the geothermal power plant, the susceptibility of the alloys to stress corrosion cracking should be tested and in situ experiments should be performed.
The composites combining aluminum and silica nanoparticles with the addition of tetramethylammonium hydroxide (Al-SiO2(T)) and butanol (Al-SiO2(B)) as mixing media have been successfully fabricated. Corrosion behavior of Al-SiO2 composites before and after exposure in 1M NaCl solution was examined using potentiodynamic polarization (Tafel curve analysis). The study was also equipped with scanning electron microscopy (SEM), energy dispersive X-ray (EDX), and X-ray diffraction (XRD) investigations. Before exposure, Al-SiO2(T) exhibited the best corrosion resistance. Performance improvement was indicated by Al-SiO2(B) up to 10 times better than Al-SiO2(T) after exposure. The increased SiO2 content did not significantly enhance the corrosion resistance of the composites. The Al-SiO2 composites with 5% SiO2 content showed very high corrosion resistance (as the optimum composition). Furthermore, pitting corrosion was observed in the Al-SiO2 composites, indicated by the formation of corrosion products at grain boundaries. The product was affected by the presence of SiO2 in the Al matrix and the NaCl environment at 90 °C (approach to synthetic geothermal media: Na+, Cl, H+, OH-). Our study revealed the presence of γ-Al2O3, γ-Al(OH)3, and Al(OH)2Cl as the dominant corrosion products.
Fitz's Atlas of coating surveys is designed as loose‐leave binder with a resistant cover that not only provides the possibility of updating the Atlas easily but also makes it practicable for on‐site use. This binder is well structured by sheet dividers with tabs for each of the 16 chapters.
All in all, this atlas supports the surveyor by giving practicable hints and advice, lists and pictures to prepare and conduct investigations and write surveys.
The fabrication and characteristics of amorphous silica reinforced Al matrix composites are studied in this paper. The major starting materials were commercial Al powder and extracted nanoparticle SiO2 (NPS) powder from Indonesian silica sands. Two different active solutions,namely N-butanol and tetramethylammonium hydroxide (TMAH), were introduced during synthesis. Characterisations in terms of physical, mechanical, microstructural and corrosion rate examinations were also employed. Introducing the SiO2 nanoparticles into the Al matrix has decreased the density and increased the porosity of the composites. The addition of N-butanol into Al/SiO2(Al/SiO2(B)) led to broader and lower X-ray diffraction profiles than the addition of TMAH (Al/SiO2(T)). From the microstructural analysis, we found that the SiO2 particles enter and agglomerate into the opening gap of the Al sheets. Furthermore, yield strength, ultimate compression strength and modulus of elasticity tended to reduce the addition of SiO2. The corrosion rate of Al/SiO2(T) was lower than that of Al/SiO2(B) composites.
Interfacial properties related to wettability and corrosion in CO2 transport pipelines are experimentally determined by the sessile and the pendant drop methods. The contact angle of a water drop in a compressed CO2 atmosphere is analyzed on an X70 pipeline carbon steel and compared to that on a martensitic steel S41500 to elucidate the effect of corrosion process on active wetting behaviour. The measurements are performed with liquid CO2 at 278 K and pressures ranging from 5 to 20 MPa. The results show that the contact angle (CA) increases with pressure from 132 ° to 143 ° for S41500 and from 117 ° to 137 ° for X70 and decreases with drop age by 20 ° to 24 ° regardless of the pressure and of the fact that corrosion only occurs on X70, which is confirmed by scanning electron microscopy, element mapping and energy dispersive x-ray spectrometry (EDS) analysis. At higher pressure, the contact angles on both materials converge. Further, related properties like density and interfacial tension were determined. CO2 - saturated water has a higher density than pure water: At 5 MPa saturated water reaches a density of 1017 kg⋅m^(-3) and at 20 MPa 1026 kg⋅m^(-3) compared to pure water with a density of 1002 kg⋅m^(-3) and 1009 kg⋅m^(-3), respectively. In this pressure range the IFT drops from 33 mN⋅m^(-1)at 5 MPa to 23 mN⋅m^(-1) at 20 MPa.
Der Vortrag berichtet über die Auslagerung von Standardproben nach DIN EN ISO 9223 bis 9226 aus Zink, Stahl, Kupfer und Aluminium auf den verschiedenen atmosphärischen Bewitterungsständen der Bundesanstalt für Materialforschung und -prüfung (BAM). Im Vortrag werden die Masseverluste, Korrosionsgeschwindigkeiten und Korrosivitätskategorien der Standardproben im freibewitterten und überdachten Bereich nach einem Jahr vorgestellt und Unterschiede hinsichtlich der Atmosphärenbedingungen aufgezeigt. Freibewitterte Proben zeigen dabei deutliche Unterschiede hinsichtlich ihres Korrosionsverhaltens im Vergleich zu überdachten Proben. Die ermittelten Korrosivitätskategorien sind sowohl standort- als auch materialspezifisch.
Depending on the CO2 generating and the capture process as well as on consecutive purification steps applied, CO2 streams from different emitters may differ in their composition. When CO2 streams with different compositions are fed into a larger pipeline network, there are several aspects that must be considered: i) chemical reactions, such as acid formation, may occur within the joint CO2 stream; ii) there may be a variation of mass flow rate and CO2 stream composition within the pipeline network if the feed-in behavior of different CO2 sources changes with time. Potential impacts of changing CO2 stream compositions and mass flow rates in CCS cluster systems were investigated in the collaborative project "CLUSTER" (see also www.bgr.bund.de/CLUSTER). In this presentation, we focus on the experimental investigations of formation and condensation of strong acids and their impacts on the corrosion of pipeline steels. When SO2, NO2, O2 and H2O are present simultaneously in CO2 streams chemical cross-reactions may occur leading to the formation of strong acids such as sulfuric and nitric acid. To prevent this acid formation the concentration of at least one of these four impurities must be kept very low (e.g., Rütters et al., 2016). At temperatures below the acid dew point temperature, acids will condense, e.g., on pipeline steel surfaces. In turn, these acid condensates may trigger steel corrosion. To better understand the process of acid formation and condensation and its implications for steel corrosion, exposure tests were performed on pipeline steel X70 in dense CO2 with varying SO2, NO2 and O2 concentration under high pressure and at 278 K in an observable autoclave, in which water was added as droplets or as vapor. Further, electrochemical tests were carried out with X70 specimens immersed in 500 mL CO2-saturated synthetic condensate solution or in droplets of the same solution on the specimen’s surface. Depending on impurity concentrations in the CO2 streams, condensates consisting of different relative amounts of nitric and sulfuric acid were formed. In condensates containing both nitric and sulfuric acid, corrosion rates were higher than the sum of those of the individual acids. In addition, corrosion products and forms depended on the condensate composition. Investigations of water droplets on steel surfaces in impurity-containing dense-phase CO2 revealed the diffusion of SO2 and NO2, followed by cross-reactions forming corresponding acids. An increase in droplet size (from 1 to 5 µl) lead to higher corrosion rates. However, in comparison to measurements in bulk solution, corrosion reactions in droplets resulted in thick, high-resistance corrosion products and observed droplet corrosion rates were significantly lower. In addition, the possibility of acid droplet formation and growth in impure liquid CO2 is influenced by the wetting behavior of the acid droplet on the steel surface. Thus, the contact angle between a water droplet and the surface steel specimens in a CO2 atmosphere was investigated in a high pressure view cell following the sessile drop method. The contact angle wasand found to be larger at higher CO2 pressures (studied from 5 to 20 MPa) and at higher temperatures (e.g. 278 K to 333 K). Further, measured contact angles were larger on rough than on smooth metal surfaces. In addition, acid formation reduced the contact angle, i.e. lead to better wetting, thereby stimulating condensation that was followed by a corrosion process. These detailed insights on the complex interplay of acid formation, condensation, wetting behavior and corrosion allow a better assessment of material suitability for pipeline transportation of impure CO2 streams
Ageing at 600 °C (from 0.1 h up to 20 h) leads to the formation of precipitations at the ferrite-ferrite (α/α) and ferrite-austenite (α/γ) grain boundaries of the lean duplex stainless steel (LDSS) X2CrNiN22-2. This leads to sensitisation due to chromium depletion and decreased pitting corrosion resistance proven by the results of various electrochemical methods (DL-EPR and determination of CPT, Epit). These results were compared with the KorroPad method, which uses an agar-based gel-electrolyte for the detection of stainless steel surfaces prone to pitting corrosion. However, the standard configuration of the KorroPad showed no differentiation for the various ageing conditions. Therefore, modified versions of the KorroPad with two, five and ten times higher NaCl and potassium ferrocyanide III (K3[Fe(CN)6]) concentrations were successfully used to visualise the behaviour detected by DL-EPR, Epit and CPT. Therefore, the KorroPad method can also detect a microstructure related reduction of pitting corrosion resistance, which can drastically reduce the experimental effort to generate sensitisation diagrams for stainless steels.
Der Vortrag berichtet über die Auslagerung von Standardproben nach DIN EN ISO 9223 bis 9226 aus Zink, Stahl, Kupfer und Aluminium auf den verschiedenen atmosphärischen Bewitterungsständen der Bundesanstalt für Materialforschung und -prüfung (BAM). Im Vortrag werden die Masseverluste, Korrosionsgeschwindigkeiten und Korrosivitätskategorien der Standardproben im freibewitterten und überdachten Bereich nach einem Jahr vorgestellt und Unterschiede hinsichtlich der Atmosphärenbedingungen aufgezeigt. Freibewitterte Proben zeigen dabei deutliche Unterschiede hinsichtlich ihres Korrosionsverhaltens im Vergleich zu überdachten Proben. Die ermittelten Korrosivitätskategorien sind sowohl standort- als auch materialspezifisch.
Ziel des Projektes ist die Qualifizierung von Duplexstählen in Tunnelbauwerken um die Einsatzmöglichkeiten alternativer nichtrostender Stähle zu den bislang gebräuchlichen rostfreien Edelstählen 1.4404 und 1.4571 zu eruieren. Da Duplexstähle im Vergleich zu austenitischen Stählen über eine doppelt so hohe Festigkeit verfügen, können Bauteile schlanker konstruiert werden, wodurch Material eingespart werden kann. Neben der Wirtschaftlichkeit muss die Dauerhaftigkeit untersucht werden. Dazu wurden speziell konzipierte Wand- und Deckenracks mit unterschiedlichen metallenen Werkstoffen und Oberflächen hergestellt und in den Tunnelbauwerken montiert. Nach bestimmten Auslagerungszeiten von bis zu drei Jahren werden die Proben demontiert und auf ihr Korrosionsverhalten untersucht. Ein weiteres Ziel neben der Qualifizierung der Werkstoffgruppe sind die Reduktion der Instandsetzungs- und Wartungsmaßnahmen der Tunnelbetreiber.
This textbook fulfills its dedication of being the “essential reference for the field, featuring protocols, analysis,fundamentals and the latest advances” of impedance spectroscopy to its readers. It really provides an insight in all facets of this powerful technique.
It should not be missed in the bookshelf of electrochemists and all other interested researchers and engineers who want to be on the current state of this technique.
Compatibility of polymeric materials with heating oil/biodiesel blends at different temperatures
(2019)
Materials compatibility is a major concern whenever the fuel composition is changed. The question arises of whether polymeric materials are resistant to heating oil with admixtures of 10 % biodiesel (B10) and 20 % biodiesel (B20).
The polarity of biodiesel increases its solvency and facilitates permeation and extrac-tion. Solvation, swelling and/or extraction lead to changes in the physical properties and chemical changes of polymeric materials.
The objective of this research was to determine the resistance of frequently used sealing materials such as FKM, EPDM, CR, CSM, NBR, IIR, VMQ, FVMQ, PA and PUR in up to four-year aged B10 for 84 days at 20 °C, 40 °C and 70 °C.
The polymeric materials: ACM, FKM, HNBR, PA, PE; POM, PUR and PVC were ex-posed to B20 for 84 days at 40°C and 70°C in another research project.
Mass, tensile strength, breaking elongation and Shore hardness A (D) of the test specimens were determined before and after the exposure for 84 (42) days in the heating oil blends B10 and B20.
There is not determined a threshold for the reduction in tensile properties and Shore hardness in the international standards. Therefore, a threshold of 15 % was deter-mined for the evaluation of the compatibility.
Measurements of the variations in mass, tensile properties and Shore hardness after exposure of the polymers in non-aged and aged heating oil B10 showed clearly that FKM, FVMQ and PA were the most resistant materials in B10. The elastomers CR, CSM, EPDM, IIR, NBR and VMQ were generally not resistant to B10. Damage to the materials increased with higher test temperatures and the age of B10.
FKM, POM and PVC showed high compatibility in B20 at 40°C and 70 °C. ACM, HNBR and PA were evaluated as resistant in B20 at 40 °C but not at 70°C.
Unter Passivität versteht man den Korrosionsschutz durch dünne, festhaftende Schichten aus Korrosionsprodukten. Für den schadensfreien Einsatz nichtrostender Stähle ergeben sich daraus zwei grundsätzliche Anforderungen.
Erstens muss sich die Passivschicht vollständig ausbilden können. Dabei sind die Oberflächenausführung,die mechanische Bearbeitung,die Elementverteilung, Ausscheidungen, die Wärmeeinbringung z.B. bei der schweißtechnischen Verarbeitung, Anlauffarben, sowie die chemische Nachbehandlung bzw. Konditionierung der Oberflächen von großer Bedeutung. Zweitens muss die Repassivierung von möglichen Defektstellen unter den Einsatzbedingungen möglich sein. Für das Repassivierungsvermögen sind die Legierungszusammensetzung, mögliche kritische Betriebszustände, prozessbedingte Besonderheiten wie etwa Stagnationsbedingungen und Reinigungsprozesse von Bedeutung.
Durch das alkalische Porenwassermilieu ist Stahl im Beton vor Korrosion geschützt. Unter ungünstigen Umgebungsbedingungen (Karbonatisierung, Chlorideintrag) kann die passive Deckschicht auf der Stahloberfläche zerstört werden. Im weiteren Verlauf können sich korrosionsbedingte Folgeschäden, wie Risse und Abplatzungen am Bauwerk ergeben. Um notwendige Sanierungsmaßnahmen sind frühzeitige und weitgehend zerstörungsfrei ermittelte Informationen über das aktuelle Korrosionsverhalten der Stahlbewehrung von großer Bedeutung. Die Potentialfeldmessung ist ein etabliertes und weit verbreitetes Verfahren zur Beurteilung des Korrosionszustandes der Bewehrung in Stahlbetonbauwerken. Mit Hilfe dieses Verfahrens können Bereiche aktiv korrodierender Bewehrung zerstörungsfrei lokalisiert werden. In der Regel kommt diese Messmethode bei der Detektion chloridinduzierter Korrosion zum Einsatz.
This work examined the factors that influence the droplet corrosion of CO2 pipeline steels caused by oxyfuel flue gases in dense phase CO2 at 278 K, simulating the underground transport conditions. The wetting properties were studied by contact angle measurement, revealing pH and time dependency on the reactive wetting behaviors of carbon steel X70. Exposure tests with CO2 saturated water droplet on steel surface showed that the impurities (220 ppmv SO2 and 6700 ppmv O2) diffused into the droplet and then reacted with metal surfaces in dense phase condition, forming the corrosion products. The corrosion rate was confirmed strongly depending on the droplet volume as well as the SO2 concentration. Condensation experiments carried out on freshly polished coupons in CO2 with 200 ppmv H2O, 220 ppmv SO2 and 6700 ppmv O2, showed that the formation and aggregation of droplets is time and temperature dependent. At 278 K, condensation happened stronger and the corrosion products, mainly consisted of dense hydrated FeSO3/FeSO4. While at 288 K, more fluffy corrosion products consisting of iron oxide/hydroxide and hydrated FeSO3/FeSO4 were found. Further exposure tests on carbon steel coupons with different surface roughness did not reveal the difference in weight loss/gain and therefore the corrosion rate.
Recent studies have shown that even at a very low concentration of impurities (less than 100 ppmv of SO2, NO2, O2 and H2O) the droplet formation and condensation of sulfuric and nitric acids in dense phase CO2 are possible and observable. To reveal the mechanism of droplet corrosion in dense phase CO2 at high pressure and low temperature, further studies on factors that affect wettability and resulting corrosion behaviors of transport pipeline steels are needed. In this study, effects of surface morphology were investigated by varying surface roughness of carbon steel coupons exposed to CO2 stream containing impurities to measure the wettability by contact angle and to observe the condensation as well as possible droplet corrosion that followed. Other considered factors were: pH of the droplet, temperature, droplet volume, and exposure time.
According to the results of the experiments carried out, the following points can be concluded:
1. Exposure tests showed that specimens with the addition of SiO2 particles and polyaniline particles exhibit better corrosion resistance than specimens with the addition of only polyaniline particles or binder only.
2. Open circuit potential measurements showed that in the beginning of the experiments, both coatings had an open circuit potential 100 mV higher than carbon steel. Within one day of immersion, the potential of carbon steel increased significantly, indicating the formation of oxide layer. After extended exposure the carbon steel potential sat between PS1 (which had higher potential) and PS2 (which had a lower potential) and all three were in the range –600 mV to –500 mV vs Ag/AgCl.
3. Both coatings PS-1 and PS-2 were degraded with increasing exposure time, shown by the decrease of absolute impedance value at low frequency range after 2, 4, and 6 days exposure.
4. Potentiodynamic test was performed after 3 hours and 6 days exposure, and it was shown that the coating in the initial stage exhibited more passive behavior than the specimens exposed for 6 days.
By exposure and electrochemical tests in the laboratory the Cu-effect on corrosion behavior of carbon steel, high-alloyed steels and Ti-alloy can be assessed.
Critical materials specific properties were determined by static exposure and electrochemical tests in an artificial geothermal water with high salinity and low pH, containing Cu. Conclusions were drawn using characteristic potential values.
It could be shown that significant Cu-deposition and -precipitation only occurred in combination with carbon steel. High-alloyed materials (S31603, S31653, S31700, S31703, S31803 and N08904) prevent the disturbing Cu-agglomeration. Therefore, they are suitable to be chosen for future design of the piping system, either in massive or in cladded form, if formation of crevices with non-metallic materials can be excluded.
From the interactions and pitting corrosion point of view, R50400 seems to be most favorable.
Dieses Werk bietet Personen, die sich mit Gefahrgutlagerung beschäftigen einen Ansatz und ein Hilfsmittel für deren Arbeit.
Dieses Buch ist lediglich ein Nachdruck der Masterarbeit. Einer redaktionellen Überarbeitung, am besten mit Rückmeldungen von Anwendern, sieht der Rezensent mit Interesse entgegen.
This book provides an overview on research‐topics who need to be investigated when dealing with this topic, basing on the symposium in 2014. It addresses the key challenges involved in CCS materials design, processing and modelling. Readers can get an overview on topics one should consider when working in these field and selecting current Journal articles.
According to the results of the experiments carried out, the following points can be concluded:
1. Exposure tests showed that specimens with the addition of SiO2 particles and polyaniline particles exhibit better corrosion resistance than specimens with the addition of only polyaniline particles or binder only.
2. Open circuit potential measurements showed that in the beginning of the experiments, both coatings had an open circuit potential 100 mV higher than carbon steel. Within one day of immersion, the potential of carbon steel increased significantly, indicating the formation of oxide layer. After extended exposure the carbon steel potential sat between PS1 (which had higher potential) and PS2 (which had a lower potential) and all three were in the range –600 mV to –500 mV vs Ag/AgCl.
3. Both coatings PS-1 and PS-2 were degraded with increasing exposure time, shown by the decrease of absolute impedance value at low frequency range after 2, 4, and 6 days exposure.
4. Potentiodynamic test was performed after 3 hours and 6 days exposure, and it was shown that the coating in the initial stage exhibited more passive behavior than the specimens exposed for 6 days.
By exposure and electrochemical tests in the laboratory the Cu-effect on corrosion behavior of carbon steel, high-alloyed steels and Ti-alloy can be assessed.
Critical materials specific properties were determined by static exposure and electrochemical tests in an artificial geothermal water with high salinity and low pH, containing Cu. Conclusions were drawn using characteristic potential values.
It could be shown that significant Cu-deposition and -precipitation only occurred in combination with carbon steel. High-alloyed materials (S31603, S31653, S31700, S31703, S31803 and N08904) prevent the disturbing Cu-agglomeration. Therefore, they are suitable to be chosen for future design of the piping system, either in massive or in cladded form, if formation of crevices with non-metallic materials can be excluded.
From the interactions and pitting corrosion point of view, R50400 seems to be most favorable.