Crevice corrosion of stainless steels 904L, 2205 and 2507 in high-temperature sulfuric acid solution containing chlorides: Influence of metal cations

Crevice corrosion influences the integrity of materials in many industrial sectors, such as hydrometallurgy. The conditions in hydrometallurgical processes are severe, with high concentrations of sulfuric acid leachant as well as high chloride impurity, oxygen and metal cation contents. In this study, crevice corrosion behaviour of highly-alloyed austenitic and duplex stainless steels is investigated in aerated high-temperature sulfuric acid solution with 1 g/l chlorides in the presence of three types of metal cations: Fe3+, Cu2+, and Fe2+. The experimental work contained determination of the oxidizing capacity of the solutions, immersion crevice corrosion tests followed by characterization of the corrosion attack, and potentiodynamic polarization measurements. The results showed that the alloy with the highest PREN-value, 2507, was not susceptible to crevice corrosion under the test conditions. In the case of alloys 904L and 2205 of relatively equal PREN-values, the extent and nature of crevice corrosion attack was different and dependent on the ratio of activities of chlorides to sulfates and the type of metal cations. The results are presented and discussed in the light of IR drop mechanism.