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Organisationseinheit der BAM
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.
Corrosion behavior of galvanized reinforcement in chloride containing mortar and carbonated mortar
(2018)
Korrosionseigenschaften von feuerverzinktem Betonstahl unterscheiden sich grundlegend von herkömmlichen Betonstahl. In diesem Vortrag sind Beispiele für das Korrosionsverhalten in chloridhaltigen und carbonatisierten Mörteln dargestellt
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.
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.
Alkali-activated fly ash mortars were studied with regard to durability-relevant transport coefficients and the electrochemical behaviour of embedded carbon steel bars on exposure of the mortars to leaching, carbonation and chloride penetration environments. The transport coefficients differed considerably between different formulations, being lowest for a mortar with BFS addition, but still acceptable for one of the purely fly ash-based mortars. Leaching over a period of ~300 days in de-ionized water did not lead to observable corrosion of the embedded steel, as shown by the electrochemical data and visual inspection of the steel. Exposure to 100 % CO2 atmosphere caused steel depassivation within approx. two weeks; in addition, indications of a deterioration of the mortar were observed. The results are discussed in the context of the different reaction products expected in high- and low-Ca alkali-activated binders, and the alterations caused by leaching and carbonation.