The Effect of Metallic Cations on the Corrosion of Iron and Tin in Boiling Acids

Abstract

In the presence of metallic cations in both boiling 0.2M citric acid and the rate of corrosion of tin was apparently determined solely by the cathodic hydrogen evolution reaction. The corrosion potential vs. log corrosion rate curves obtained for iron in 0.2M citric acid in the presence of various cations were complex, and 5 types of behavior were observed: (a) activation of the cathodic reaction, such as obtained with nickel, rhodium, ruthenium, iridium, and platinum; (b) activation of the anodic reaction such as observed with antimony and by bubbling oxygen through the solution; (c) inhibition of the anodic reaction such as observed with tin, lead, and indium; (d) inhibition of the cathodic reaction such as observed with mercury and cadmium; and (e) inhibition of both the anodic and cathodic reactions such as observed with arsenic. Effective inhibition of corrosion of iron in contact with tin in 0.2M citric acid was only obtained under conditions where the Sn(II) ions came in contact with the iron surface.