The Effects of Nitrogen on the Passivity and the Pitting Corrosion of Stainless Steels

概要

論文の詳細を見る
The effects of nitrogen alloying on the passivity and the pitting corrosion resistance of stainless steels are reviewed and discussed. Nitrogen in the solid solution of austenitic stainless steels is enriched at the passive film/metal matrix interface or at the metal side in the film. The effects of nitrogen alloying on the passivating ability estimated by the critical current density (icrit) in the acid is variable; they depend on the alloy composition and the electrolyte conditions. Alloying nitrogen in general seems to lower icrit when the base steel shows a high value of icrit (above ca. 1mA/cm2). Nitrogen enriched on surface of stainless steels helps passivation of a micropit by preventing the lowering of pH in it before the steadily growing condition is established. Duplex stainless steel shows an optimum pitting corrosion resistance at an appropriate α/γ phase ratio determined by the amount of the favorable alloying elements (i.e. Cr, Mo and N). This can be explained by the partitioning of these elements in each phase.
社団法人腐食防食協会の論文