Abstract
High-pH SCC occurs through mechanical rupture of an oxide film, followed by active intergranular corrosion at the crack tip and subsequent film repair. Oxide film strain properties have important implications in the high-pH crack growth process, but have never been determined in high-pH SCC environments. The self-healing properties of the oxide may be affected by loading and unloading time, strain rates, as well as by environment. Further knowledge of the film strain and the corrosion event that takes place as the film ruptures will improve our understanding of the important parameters determining high-pH SCC, and improve the prediction of crack growth rate distributions. In this work, film rupture was monitored by current noise under a constant applied potential in scratching electrode experiments, slow strain rate and cyclic loading experiments. The results suggest that successive damaging cycles are likely to cause more damage, result in more film rupture events and higher crack growth rates than damaging cycles that are separated by sufficient time to fully repassivate the film and dissipate creep.
