Studies on Corrosion Products of Fe-Cu-Sb, Fe-Cu-Se, Fe-Cu-Sn and Fe-Cu-As Alloy Systems in Sulfuric Acid

Abstract

Investigations were made on the relation between the corrosion behavior and the corrosion products of steels in 40% sulfuric acid at 60°C. The difference of effects among the alloying elements (Sb, Se, As and Sn) on corrosion products were analyzed by means of chemical analysis and X-ray diffraction. The effects of metallic ions (Sb³⁺, Se⁶⁺, As⁵⁺ and Sn⁴⁺) on the corrosion of Fe-0.3%Cu alloy in 40% sulfuric acid at 60°C were also investigated, and the following results were obtained.
(1) Antimony formed an intermetallic compound (Cu₂Sb) together with copper in steel. This compound was concentrated in the corrosion product film, and inhibited both anodic and cathodic reactions, thus suppressing the corrosion of steel in sulfuric acid.
(2) Arsenic was effective on anodic inhibition by redeposition like copper. In this case, the combined effect with copper was not found.
(3) Selenium had both properties of antimony and arsenic and formed an intermetallic compound with copper. But the individual effect was stronger than the combined effect with copper.
(4) The effect of tin was scarecely observed even in the presence of copper.