Re-Oxidation Behavior of Cr and V Ions in the Boiling Nitric Acid Solution and Acceleration Effect on Corrosion Rate of Stainless Steel

Abstract

In order to clarify the acceleration effect of corrosion with small amount of oxidizing ion addition in boiling nitric acid solution, Cr(VI) and V(V) ions added solution were examined Cr(VI) and/or V(V) added nitric acid solutions accelerated corrosion rates of SUS304ULC. The acceleration effect of Cr was larger than that of V. Although the acceleration effect of Cr rapidly decreased, that of V stayed constant. Concentration of Cr(VI) in the solution was decreased correspond to the corrosion rate. Re-oxidation of V is faster than that of Cr. Cr(VI) ions are reduced to Cr(III) by corrosion reaction of SUS340ULC but a little amount of them are re-oxidized. On the other hand, V(V) ions are also reduced to V(IV) and almost of all of them are re-oxidized to V(V). So, corrosion rate of V added solution stayed constant and that of Cr added decreased.