The Effect of Products of Nitrate Ion Reduction on the Kinetics of Electrode Reactions on Stainless Steel

The effects of nitrate ions and possible products of their reduction (ammonium, hydrazine, and hydroxylammonium ions) on electrochemical characteristics of stainless steel are studied in phosphoric acid. Specific properties of nitrates as corrosion inhibitors of a passivating type are explained by a complex effect of their reduction products on the kinetics of both cathodic and anodic reactions. It is found that the products of nitrate reduction, firstly, accelerate cathodic reactions, secondly, accelerate anodic reactions due to the formation of complexes with the ions of corroding steel, and, thirdly, reducte passivation potential due to alkaline properties of certain products. Everything aforementioned substantially affects the possibility of using nitrates as the corrosion inhibitors of stainless steel in acidic media.