The Selective Dissolution of SUS304 and SUS316 Austenitic Stainless Steels in a Hydrochloric Acid Solution

Nishimura Rokuro, Araki Michio, Kudo Kiyokatsu

doi:10.2320/jinstmet1952.47.5_413

The anodic behavior and selective dissolution of SUS304 and SUS316 austenitic stainless steels were investigated as a function of potential in a 1 kmol·m⁻³HCl solution by using electrochemical technique and Inductively Coupled Plasma Emission Spectrometry (ICP).<BR>On the basis of the comparison between the amount of total anodic charge passed and that of electric charge obtained from dissolution, it was found that the anodic polarization curves of SUS304 and SUS316 were divided into three regions, the active dissolution, the film formation, and the film destruction. The compositions of metal ions dissolved in the solution revealed that the preferential dissolution of Fe took place on both steels in the active dissolution region and led to the enrichment of Cr on SUS304 surface and that of Cr, Ni and Mo on SUS316 surface. In the region of the film formation, it was found that a film formed on SUS304 was enriched with Cr because of the preferential dissolution of Fe. In the case of SUS316, it was suggested in terms of the preferential dissolution of Ni and Mo that a film changed from Cr, Ni, Mo-rich layer into Cr-rich layer during anodic oxidation.<BR>It was, furthermore, deduced that Mo lowered the activity or density of active centers such as MnS on SUS316 surface in the process of active dissolution and consequently contributed to the formation of a uniform film free from defects.

The Selective Dissolution of SUS304 and SUS316 Austenitic Stainless Steels in a Hydrochloric Acid Solution

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