Pitting Corrosion of 18Cr-8Ni Stainless Steel

I . Factors controlling pitting corrosion and laboratory methods used for its study are reviewed. An electrolytically accelerated test was developed for investigation of pit initiation. A controlled direct current was passed through a cell whose anode was the stainless steel specimen and whose electrolyte was the pitting solution. The number of pits formed depended on the current density, the steel specimen (composition and surface treatment), and the solution (composition and temperature). II . The accelerated electrolytic pitting method described in Part I was used to determine the influence of alloying elements added to 18Cr‐8Ni stainless steel on pit initiation in sodium chloride and bromide solutions. Reduction in carbon content, increase in nitrogen content of these steels, and alloying additions of molybdenum and silicon increased resistance to pit initiation. Grain boundaries, rather than nonmetallic inclusions, were primary sites of pit initiation during simple immersion or in the eleetrolytically accelerated test.