The electrochemical behaviour of 9Cr-1Mo steel in concentrated acid solution mixtures

The electrochemical polarization behaviour of 9Cr-1Mo steel has been investigated in binary and ternary mixtures of concentrated phosphoric acid, acetic acid, sulphuric acid, and formic acid at 20 ± 1 °C. The steel showed active-passive and transpassive behaviour in all solutions. The alloy surface...

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Bibliographic Details
Published in:Corrosion science 1998-04, Vol.40 (4), p.705-713
Main Authors: Singh, V.B., Upadhyay, B.N.
Format: Article
Language:English
Subjects:
Applied sciences
concentrated acids mixture solution
Corrosion
Corrosion environments
electropolishing
Exact sciences and technology
Metals. Metallurgy
transpassive dissolution
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Summary:The electrochemical polarization behaviour of 9Cr-1Mo steel has been investigated in binary and ternary mixtures of concentrated phosphoric acid, acetic acid, sulphuric acid, and formic acid at 20 ± 1 °C. The steel showed active-passive and transpassive behaviour in all solutions. The alloy surface exhibited a tendency to undergo electropolishing in acetic acid-based phosphoric acid electrolytes. In the transpassive region, a current plateau was always observed but electropolishing occurred only in a few selected mixtures (10–20 volume percent acetic acid + balance phosphoric acid). The experimental results reveal that electropolishing is under mass transport control and the existence of a current plateau is not a sufficient condition. A low content of water is beneficial for electropolishing.
ISSN:0010-938X
1879-0496
DOI:10.1016/S0010-938X(97)00172-8