Dehnungsinduzierte Korrosionsprozesse

Strain-induced corrosion phenomena When investigating stress corrosion cracking phenomena in the past, application of a static load σ played a major role in the performance of experiments. A further influencing factor, to which until now was payed less attention, is the strain ? caused by a mechanical stress. Increasing attention is payed also to the variations with time of these influencing factors, \documentclass{article}\pagestyle{empty}\begin{document}$ \dot \sigma $\end{document} and \documentclass{article}\pagestyle{empty}\begin{document}$ {\dot \varepsilon }$\end{document}. A strain, induced by a load may have the following effects: (i) break-up of a protective layer and/or (ii) mechanical stimulation of anodic metal dissolution. Both types of failures are discussed. The type of failure (i) is referred to as stress-induced, the type of failure (ii) as strain-induced corrosion. The authors discuss the question, whether type of failure (ii) is always involved in stress corrosion cracking. For some corroding systems, this question can clearly be answered in the negative, while in numerous systems the occurrence of stress corrosion cracking is markedly influenced by the strain rate. The relevant systems are described in detail. Essential for the authors' considerations is the existence of an upper and lower critical strain rate for the occurrence of stress corrosion cracking. Transition from strain-induced stress corrosion cracking to corrosion fatigue is given with relatively high upper critical strain rates. From the influence of strain rate upon stress corrosion cracking, conclusions are derived for the application of test methods for detecting susceptibility of metallic materials to stress corrosion cracking.