TY - JOUR A1 - Mietz, Jürgen A1 - Isecke, Bernd T1 - Assessment of test methods for evaluation stress corrosion cracking susceptibility of prestressing steels JF - Materials and corrosion N2 - Prestressing steels can be exposed in prestressed concrete structures in construction stage (ungrouted duct) to environmental conditions causing formation and growth of hydrogen induced cracks with brittle fracture of the steel. The risk of this hydrogen induced stress corrosion cracking can be minimized by appropriate treatment, but there is a requirement for construction to approve only prestressing steel having no enhanced susceptibility to stress corrosion cracking. The paper describes the historical development of the different test methods proposed in the past and gives an overview on the general requirements for a suitable test method to assess the hydrogen-induced stress corrosion susceptibility of prestressing steels. Since 1982, based on investigations on construction sites and transfer of the results into laboratory tests, a test method is available enabling realistic estimation of suitable application possibilities of prestressing steels. This so called DIBt-test is approved to distinguish between prestressing steels susceptible to hydrogen induced stress corrosion cracking and those suitable and therefore approvable steels at practical environmental conditions. Furthermore the test enables estimation of corrosion risk for newly developed prestressing steels with higher strength. Translated Abstract Beurteilung der Prüfverfahren zur Untersuchung der Spannungsrisskorrosionsempfindlichkeit von Spannstählen Spannstähle können in Spannbetonbauwerken im Bauzustand (unverpresstes Hüllrohr) Umgebungsbedingungen ausgesetzt sein, die zur Bildung und Ausbreitung wasserstoffinduzierter Risse mit Sprödbruch des Stahles führen können. Das Risiko dieser wasserstoffinduzierten Spannungsrisskorrosion kann einerseits durch eine sachgemäße Verarbeitung der Spannstähle minimiert werden, andererseits besteht die Notwendigkeit nur solche Spannstähle für die Baupraxis zuzulassen, die unter baupraktischen Bedingungen keine erhöhte Empfindlichkeit für Spannungsrisskorrosion besitzen. Die vorliegende Arbeit beschreibt die historische Entwicklung der verschiedenen vorgeschlagenen Prüfverfahren und gibt einen Überblick über die allgemeinen Anforderungen an ein geeignetes Verfahren zur Beurteilung der wasserstoffinduzierten Spannungsrisskorrosionsempfindlichkeit von Spannstählen. Seit 1982 steht, begründet durch Untersuchungen auf Baustellen und Umsetzung der Ergebnisse in Laborversuchen, ein Prüfverfahren zur Verfügung, das eine wesentlich realistischere Einschätzung der Einsatzmöglichkeiten von Spannstählen zulässt. Dieser sog. DIBt-Test hat sich bewährt, um unter praktischen Umgebungsbedingungen gegen H-induzierte Spannungsrisskorrosion empfindliche Spannstähle von geeigneten und damit zulassungswürdigen Stählen zu unterscheiden. Des weiteren erlaubt die Prüfung ebenfalls eine Abschätzung des Korrosionsrisikos für neuentwickelte, höherfeste Spannstähle. PY - 2002 SN - 0947-5117 SN - 1521-4176 VL - 53 IS - 6 SP - 373 EP - 384 PB - Wiley-VCH Verl. CY - Weinheim AN - OPUS4-1402 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Broomfield, J. A1 - Fischer, Joachim A1 - Mietz, Jürgen A1 - Schneck, U. T1 - Case studies JF - Materials and corrosion N2 - In this paper, some quite different survey tasks are described, and it can be seen that corrosion surveys will follow a certain scheme of data acquisition (first NDT measurements, than detailed testing on suspect areas), but the individual scope of on-site measurements may have a vast variety according to the local circumstances, and the interpretation always has to refer to a wider set of information than the data readings only. KW - Corrosion surveys KW - Non-destructive testing KW - Reinforcement KW - Concrete KW - Potential mapping KW - Corrosion PY - 2013 DO - https://doi.org/10.1002/maco.201206649 SN - 0947-5117 SN - 1521-4176 VL - 64 IS - 2 SP - 147 EP - 160 PB - Wiley-VCH Verl. CY - Weinheim AN - OPUS4-29730 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Fischer, Joachim A1 - Burkert, Andreas A1 - Mietz, Jürgen T1 - Case studies of stainless steel corrsoion in indoor swimming pool environments JF - Corrosion engineering, science and technology N2 - In indoor swimming pools stainless steels are used not only due to structural and economic reasons but also due to aesthetic considerations. And therefore not only safety relevant load bearing components have to fulfil their tasks but also the visual appearance should be free of any staining. In a lot of cases basic requirements (e.g. design criteria, material selection and maintenance) being essential parts of technical regulations were not taken into account. Typical case studies with explanation of the cause of the corrosion problems and possibilities to prevent them are shown in the present paper. KW - Stainless steel KW - Atmospheric corrosion KW - Indoor swimming pools PY - 2011 DO - https://doi.org/10.1179/174327809X409150 SN - 1478-422X VL - 46 IS - 1 SP - 76 EP - 79 PB - Maney Publishing CY - London, UK AN - OPUS4-23287 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Gluth, Gregor A1 - Ebell, Gino A1 - Hlavacek, Petr A1 - Mietz, Jürgen T1 - Chloride‐induced steel corrosion in alkali‐activated fly ash mortar: Increased propensity for corrosion initiation at defects JF - Materials and Corrosion N2 - Chloride contents at the steel–mortar interface that initiate steel corrosion were determined for carbon steel in alkali‐activated fly ash mortar for three different exposure conditions: exposure to 1 M NaCl solution; leaching in deionized water and then exposure to 1 M NaCl solution; and leaching in deionized water, aging in air at 20°C and natural CO2 concentration, and then exposure to 1 M NaCl solution. For comparison, a Portland cement mortar, exposed to 1 M NaCl solution, was studied. The median values of the corrosion‐initiating chloride contents (average over the full length of the rebar) in the alkali‐activated fly ash mortar varied between 0.35 and 1.05 wt% Cl with respect to binder, consistently lower than what was obtained for the Portland cement mortar, but with no clear trend regarding the exposure conditions. For most of the alkali‐activated fly ash mortar specimens, preferential corrosion at the connection between the working electrode and the external measurement setup was observed, while preferential corrosion did not occur for the Portland cement mortar. Scanning electron microscopy and auxiliary experiments in synthetic solutions indicated that this behavior was caused by inhomogeneities at the steel–mortar interface in the alkali‐activated mortar, likely due to its peculiar rheological properties in the fresh state. KW - Alkali-activated materials KW - Steel corrosion KW - Critical chloride content KW - Steel-concrete interface PY - 2020 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-507268 DO - https://doi.org/10.1002/maco.202011541 VL - 71 IS - 5 SP - 749 EP - 758 PB - Wiley-VCH AN - OPUS4-50726 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Burkert, Andreas A1 - Lehmann, Jens A1 - Burkert, Annette A1 - Mietz, Jürgen T1 - Damage of stainless steel bars due to atmospheric corrosion JF - Materials and corrosion N2 - In addition to constructional requirements in civil engineering stainless steels often have to fulfil high visual demands. Unexpected impairments of the visual appearance of stainless steels under low corrosive conditions are a widespread problem today. Frequently it is supposed that this is caused by changes in the alloy composition, worse environmental conditions or improper handling. Within a research project the systematic investigation of several cases of damaged stainless steel bars has shown that the reasons are based on well-known material defects like chemical inhomogeneities (e.g. precipitations or local carburization) or geometrical defects (e.g. undercuts, rolling defects or shell formation). Thus, the failures could be clearly identified as production failures of the respective semi-finished products. KW - Atmospheric corrosion KW - EPR test KW - Failure KW - Intercrystalline corrosion KW - Stainless steel KW - Nichtrostender Stahl KW - Werkstoffauswahl KW - Dauerhaftigkeit KW - Korrosion PY - 2012 DO - https://doi.org/10.1002/maco.201005701 SN - 0947-5117 SN - 1521-4176 VL - 63 IS - 3 SP - 264 EP - 270 PB - Wiley-VCH Verl. CY - Weinheim AN - OPUS4-25702 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Mayer, T. F. A1 - Dauberschmidt, C. A1 - Bruns, M. A1 - Eichler, T. A1 - Wiens, U. A1 - Mietz, Jürgen A1 - Gehlen, C. A1 - Ebell, Gino A1 - Gerhard, G. A1 - Osterminski, K. T1 - Das Instandsetzungsprinzip W-Cl JF - BAutechnik N2 - Während das Instandsetzungsprinzip W bei carbonatisierungsinduzierter Korrosion seit vielen Jahren als Standardverfahren etabliert ist, wird seine Anwendbarkeit bei chloridinduzierter Korrosion (W-Cl) in der Fachwelt bis heute kontrovers diskutiert. Zwar ergeben sich aus seiner Anwendung gegenüber anderen Instandsetzungsverfahren auf den ersten Blick u. U. deutliche wirtschaftliche Vorteile, allerdings besteht bei diesem Verfahren ein deutlich höheres Risiko, dass das Instandsetzungsziel nicht erreicht wird. Im vorliegenden Beitrag werden die technischen Grundlagen des Instandsetzungsprinzips W-Cl sowie der aktuelle Kenntnisstand - sowohl für den gerissenen als auch für den ungerissenen Beton - dargestellt und baurechtliche Konsequenzen, die sich aus dem erhöhten Ausführungsrisiko ergeben, diskutiert. Korrosionsmonitoring als Element zum Nachweis des Instandsetzungserfolgs bei Anwendung des Prinzips W-Cl wird vorgestellt. Anhand von Anwendungsbeispielen werden sowohl die Risiken, die mit dem Verfahren verbunden sind, als auch das Potenzial bei erfolgreicher Anwendung veranschaulicht. KW - Korrosion KW - Instandsetzung KW - W-Cl KW - Risse PY - 2020 DO - https://doi.org/10.1002/bate.201900083 SN - 0932-8351 VL - 97 IS - 1 SP - 2 EP - 10 PB - Ernst & Sohn CY - Berlin AN - OPUS4-50246 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Ebell, Gino A1 - Burkert, Andreas A1 - Mietz, Jürgen T1 - Detection of reinforcement corrosion in reinforced concrete structures by potential mapping: Theory and practice JF - International Journal of Corrosion N2 - Electrochemical potential mapping according to guideline B3 of DGZfP (German Society for Nondestructive Testing) is a recognized technique for the localization of corroding reinforcing steels. In reinforced concrete structures the measured potentials are not necessarily directly linked to the corrosion likelihood of the reinforcing steel. The measured values may be significantly affected, different from, e.g., stress measurement, by different influences on the potential formation at the phase boundary metal/concrete itself as well as the acquisition procedure. Due to the complexity of influencing factors there is a risk that the results are misinterpreted. Therefore, in a training concept firstly the theoretical basics of the test method should be imparted. Then, frequently occurring practical situations of various influencing factors will be made accessible to the participants by a model object specially designed for this purpose. The aim is to impart profound knowledge concerning the characteristics of potential mapping for detecting corrosion of reinforcing steel in order to apply this technique in practice as reliable and economical test method. KW - Corrosion KW - Potential mapping KW - Korrosion KW - Potentialfeldmessung PY - 2018 DO - https://doi.org/10.1155/2018/3027825 SN - 1687-9333 SN - 1687-9325 VL - 2018 SP - Article 3027825, 1 EP - 6 PB - Hindawi AN - OPUS4-46206 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Mietz, Jürgen A1 - Burkert, Andreas A1 - Eich, Gerd A1 - Raupach, M. T1 - Development of a new combined corrosion protection system for chloride-contaminated reinforced concrete structures JF - Materials and corrosion N2 - Chloride-induced damage of reinforcing steel is especially for parking garages and bridges often very severe as large amounts of chlorides act on horizontal surfaces which could lead to fast ingress of these detrimental ions up to the level of the reinforcement and subsequently to high rates of corrosion. In order to avoid the disadvantages of conventional rehabilitation (unreliable prognosis with patch repair or high costs and regular maintenance with cathodic protection using impressed current) a new combined protection system was developed where the principle of drying out the concrete (by means of a surface protection system) is combined with a temporary cathodic protection (by means of a sprayed zinc layer) during the transitional period of the drying out process. This new system was tested both in the laboratory and on-site at a pilot application. Based on the results obtained the possibilities and limitations of the new system are discussed in this paper. KW - Chlorid-induced corrosion KW - Reinforcing steel KW - Cathodic protection KW - Sprayed zinc layer KW - Surface protection system PY - 2005 DO - https://doi.org/10.1002/maco.200403836 SN - 0947-5117 SN - 1521-4176 VL - 56 IS - 2 SP - 104 EP - 110 PB - Wiley-VCH Verl. CY - Weinheim AN - OPUS4-7157 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Eich, Gerd A1 - Burkert, Annette A1 - Burkert, Andreas A1 - Mietz, Jürgen T1 - Einsatz des nichtrostenden Duplex-Stahls 1.4362 als preisgünstige Alternative im Bauwesen JF - Stahlbau N2 - Aufgrund der in den letzten Jahren stark angestiegenen Rohstoffpreise sind die im Bauwesen häufig eingesetzten nichtrostenden Standardaustenite in vielen Fällen nicht mehr wettbewerbsfähig. Eine deutlich kostengünstigere Alternative stellt der Duplex-Stahl 1.4362 dar, der bisher aber noch nicht bauaufsichtlich zugelassen ist. Mit Hilfe von Auslagerungsversuchen sowie elektrochemischen Untersuchungen sollte das Korrosionsverhalten dieses Werkstoffs unter neutralen bis leicht sauren, chloridhaltigen Umgebungsbedingungen, wie sie in vielen Bereichen des Bauwesens vorkommen, geklärt werden. Insgesamt belegen die Ergebnisse, dass der kostengünstigere Werkstoff 1.4362 für baupraktische Anwendungen eine Alternative für Anwendungen darstellen kann, in denen bisher die Werkstoffe 1.4404 oder 1.4571 eingesetzt wurden. KW - Duplex-Stähle KW - Nichtrostende Stähle KW - Auslagerungsversuche KW - Elektrochemische Versuche KW - Lochkorrosionspotential KW - Spaltkorrosionspotential PY - 2007 DO - https://doi.org/10.1002/stab.200710094 SN - 0038-9145 SN - 1437-1049 SN - 0932-6375 VL - 76 IS - 12 SP - 898 EP - 904 PB - Ernst CY - Berlin AN - OPUS4-16364 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Poltavtseva, Marina A1 - Ebell, Gino A1 - Mietz, Jürgen T1 - Electrochemical investigations of carbon-based conductive coatings for application as anodes in ICCP systems of reinforced concrete structures JF - Materials and corrosion N2 - Carbon-based conductive coatings are complex composites, consisting of an organic or inorganic binder and conductive carbon components, for application as anodes in impressed current cathodic protection systems of reinforced concrete structures. The electrochemical properties of three coatings at different humidity and in saturated calcium hydroxide solution were studied by electrochemical methods, such as electrochemical impedance measurement, measuring of open circuit potential over time and galvanostatic polarization. The dissolved organic and inorganic carbons in electrolyte solution were quantified by using a photometric method. The structures of the coatings were investigated before and after the electrochemical tests by microscopy and scanning electron microscope/EDX analysis. The results of the electrochemical impedance measurements show that the tested coatings all have a relatively low resistance, which is between 100 and 200 Ω. The binder and the surface porosity influence the degradation behavior of those coatings. Especially the organic binder reacts with the strong alkaline medium under dissolving of organic carbon. KW - Cathodic protection KW - Corrosion KW - Rebar KW - Reinforcement KW - Concrete KW - Potential PY - 2015 DO - https://doi.org/10.1002/maco.201407680 SN - 0947-5117 SN - 1521-4176 VL - 66 IS - 7 SP - 627 EP - 634 PB - Wiley-VCH Verl. CY - Weinheim AN - OPUS4-33709 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -