Resistance to Pitting of Types 202 and 321 Steels to Sulfuric Acid and Sodium Chloride Solutions

Abstract

Abstract Anodic potentiokinetic polarization measurements were made of pitting corrosion of two stainless steels in 1 N sulfuric acid and 1 N sodium chloride solutions to compare then-resistance to this type of corrosive attack. One steel was approximately of the same analyses as AISI Type 321 (H18N9), the second a substitutional steel with lower nickel content containing manganese and nitrogen approximately of the same analyses as AISI Type 202 (OH17N4G8). The steels were investigated both in as-cast state and after the plastic deformation. Type H18N9 steel, in its passive potential region is somewhat less resistant to pitting, assuming that total corrosion volume is taken into account-However, the type of pits seems to be more dangerous in Type OH17N4G8 steel. A similar situation is observed with respect to the structure effect. Rolled alloys exhibit greater total pitting corrosion losses while those tested as-cast suffers less extensive over-pitting. Pits in as-cast materials are, however, deeper and larger.