The influence of pH, temperature and surface pretreatments on the stability of passive films formed on Sanicro 28 and 5R60 stainless steels in aqueous chloride solutions

• Published in: Corrosion science 1989, Vol.29 (10), p.1205-1214
• Main Authors: CARROLL, W. M, WALSH, T. G
• Format: Article
• Language: English
• Subjects: Applied sciences; chemical variables measurement; Corrosion; Corrosion mechanisms; corrosion prevention; Cross-disciplinary physics: materials science; rheology; electrochemistry; Exact sciences and technology; Materials science; Metals, semimetals and alloys; Metals. Metallurgy; Physics; Specific materials; stability; surface properties; thermal properties; thermal variables measurement
• ISSN: 0010-938X; 1879-0496
• DOI: 10.1016/0010-938X(89)90067-X

The electrochemical behaviour of a highly alloyed steel Sanicro 28 and a more common grade 5R60 were examined in aqueous chloride solutions using long term (> 60 min) potentiostatic tests. Special attention was paid to ensuring crevice free electrode assemblies. Lowering the pH to 1.0 or raising the chloride ion concentration to 3 M was found to have very little influence on the stability of passive films formed on Sanicro 28. For 5R60 on the other hand, lowering the pH (11.0 to 2.0) at a fixed chloride level (0.5 M) was found to alter quite markedly the stability of the passive films formed as evidenced by a large increase in the number of current fluctuations appearing on the current decay profiles. Reduction of the temperature of the test solution or chemical treatment of the test specimens in HNO sub(3) or HNO sub(3)/HF solutions prior to testing leads to a considerable improvement in passive film stability.