Authors: Marikkannu, C.; Sathiyanarayanan, S.; Venkatachari, G.

Source: Transactions of the Institute of Metal Finishing, Volume 83, Number 3, June 2005 , pp. 158-160(3)

Publisher: Maney Publishing

Abstract:

An attempt has been made to develop a chemical passivation treatment for AISI 304 stainless steel based on nitric acid in the presence of various oxidising agents such as sodium molybdate, potassium dichromate and potassium permanganate. The stability of the passive film formed through different chemical passivation treatments has been studied by potential–time measurement in 0·5 M sulphuric acid and the operating parameters of chemical passivation have also been optimised by this technique. Results of the study show that chemical passivation of stainless steel in nitric acid shifts the open circuit potential in the positive direction. Increase of concentration of nitric acid, treatment time and temperature further ennobles the potential. Addition of either dichromate or permanganate ions to nitric acid helps in forming a more stable passive film whereas molybdate, even at higher concentrations does not have any beneficial effect on passive film formation.

Keywords: NITRIC ACID; STAINLESS STEEL; CHEMICAL TREATMENT; PASSIVATION; SULPHURIC ACID

Document Type: Miscellaneous

DOI: http://dx.doi.org/10.1179/002029605X48879

Publication date: 2005-06-01

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