The effect of gap configuration on crevice corrosion of 316L stainless steel in chloride-containing aqueous media

In this study, crevice corrosion of 316L stainless steel with different gap configurations was studied in aqueous solutions containing 10; 9500; and 19,000 ppm chloride ion at room (25 °C) and elevated (60 °C) temperatures. It has been shown that the likelihood of crevice corrosion in the lack-of-fusion areas during welding on a backing ring increases significantly in the presence of an intermediate gap of approximately 0.2 mm located between the main technological gap with a width of 0.8–1.0 mm and a lack-of-fusion crevice with a width of 5–50 μm. In this case, corrosion occurs even at a 10 ppm concentration of chloride ions in an aqueous solution. This situation was modeled using multiple-crevice samples, in which the groove depth of the non-metallic sleeve was 0.2, 0.3, and 0.5 mm. At a groove depth of 0.2 mm, crevice corrosion occurred in an aqueous solution containing 10 ppm chloride ions. The obtained results can be explained by additional diffusion restrictions in terms of supplying/removing the matter to/from the active dissolution zone in the gap, as well as by blocking of the gap with corrosion products in the presence of an intermediate gap of a certain size.