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 - 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 - Babutzka, Martin A1 - Müller, Thoralf A1 - Mietz, Jürgen A1 - Burkert, Andreas T1 - Investigation of the influence of iron‐containing abrasives on the corrosion behaviour of the aluminium alloy AlSi1.2Mg0.4 JF - Materials and Corrosion N2 - The corrosion resistance of aluminium surfaces is closely linked to the surfacecstate after a grinding process. For years, iron‐containing abrasive materials were suspected to lead to increased corrosion susceptibility after processing of aluminium surfaces. To prove a possible correlation between the iron content of an abrasive and the corrosion behaviour of aluminium components, scientific investigations and experimentally practical corrosion tests are necessary. For the current investigation, specimens of a technical Al‐Si alloy from the same batch were used. The test specimens were mechanically ground with various resin‐bonded model abrasives containing different iron contents. The performed corrosion tests did not reveal a negative influence of the different iron‐containing abrasives on the corrosion behaviour of the Al–Si alloy. However, the most sensitive measuring method (electrochemical noise) showed differences in the surface activity depending on the type of abrasive. KW - Aluminium KW - Corrosion KW - Corrosion testing KW - Grinding PY - 2020 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-506762 DO - https://doi.org/10.1002/maco.202011657 SN - 0947-5117 SN - 1521-4176 VL - 71 IS - 10 SP - 1667 EP - 1679 PB - Wiley‐VCH Verlag GmbH & Co. KGaA CY - Weinheim AN - OPUS4-50676 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Babutzka, Martin A1 - Mietz, Jürgen A1 - Burkert, Andreas T1 - Investigation of the salinization of steel surfaces in marine environment JF - Materials and Corrosion N2 - The salinization and contamination of metal surfaces by chloride-containing aerosols is of great importance with regard to corrosion phenomena of damaged coated metal surfaces and stainless steels in the maritime sector and in offshore applications. Detailed questions have to be answered to clarify whether and to what extent salinization of the surface has an influence on the adhesion and durability of coatings in repairing applications and on pitting occurrence on stainless steels under atmospheric conditions. The questions arise which degree of salinization is reached after which period of time and how a defined and reproducible salinization can be simulated in the laboratory for further systematic investigations. The article is dedicated to these questions. Results of a field trial on the Island of Heligoland are presented and a simple procedure for a defined loading of metal surfaces with chlorides at a laboratory scale using a design of experiments (DoE) approach is introduced. KW - Maritime Atmosphäre KW - Versalzung KW - Maritime atmosphere KW - Salinization PY - 2018 DO - https://doi.org/10.1002/maco.201810636 SN - 0947-5117 SN - 1521-4176 VL - 70 IS - 6 SP - 1016 EP - 1025 PB - Wiley-VCH Verlag CY - Weinheim AN - OPUS4-47727 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Burkert, Andreas A1 - Müller, Thoralf A1 - Lehmann, Jens A1 - Mietz, Jürgen T1 - Long-term corrosion behaviour of stainless steels in marine atmosphere JF - Materials and Corrosion N2 - Nine different stainless steel alloys were exposed for 5 years under marine environment and their corrosion behaviour was compared and assessed. The investigation of four different surface finishes for all alloys tested further enabled to consider industry-specific features of the surface finish for the material comparison. The results of the exposure tests yield conclusions regarding the influence of alloy composition, surface finish and exposure duration under marine environment. The three duplex stainless steels revealed excellent corrosion resistance even in case of crevices during the 5 years of exposure under the given exposure conditions. Also the molybdenum-alloyed ferritic steel 1.4521 showed good corrosion resistance comparable to the classical austenitic materials 1.4301 and 1.4404. KW - Corrosion KW - Free weathering KW - Marine atmosphere KW - Stainless steels PY - 2018 DO - https://doi.org/10.1002/maco.201709636 SN - 0947-5117 SN - 1521-4176 VL - 69 IS - 1 SP - 20 EP - 28 PB - Wiley-VCH Verlag GmbH & Co KGaA CY - Weinheim AN - OPUS4-43625 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Mietz, Jürgen A1 - Burkert, Andreas T1 - Selection and Durability of Stainless Steels for Civil Engineering JF - Key Engineering Materials N2 - Due to the large number of stainless steels with different chemical composition and different microstructure the selection of the suitable material represents a huge challenge. In order to facilitate the appropriate grade selection, in the current European standard EN 1993-1-4 a procedure is defined based on the use of a look-up table considering the key variables that influence the selection of stainless steels. The table uses descriptions that competent designers should be able to readily understand or define without prior knowledge. The output from the look-up table is used to select alloys based on a Corrosion Resistance Class (CRC) from I to V. The advantage of this approach is that the designer simply specifies the relevant CRC and does not need to consider in detail which of the many (very similar) alloys to specify. KW - Corrosion resistance KW - Stainless steel KW - Civil engineering KW - Atmospheric corrosion PY - 2020 DO - https://doi.org/10.4028/www.scientific.net/KEM.843 SN - 1662-9795 VL - 843 SP - 125 EP - 131 PB - Trans Tech Publications Ltd, CY - Switzerland AN - OPUS4-50831 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -