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

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...

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Bibliographic Details
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
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Summary: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.
ISSN:0010-938X
1879-0496
DOI:10.1016/0010-938X(89)90067-X