Effect of endgrain attack on corrosion of 18cr-10ni austenitic stainless steel in simulated dissolver liquor

Abstract

The exposed endgrain of austenitic stainless steels displays significantly inferior corrosion resistance toward the rolling direction in nitric acid solutions. Endgrain attack is often accompanied by preferential localised corrosion which produces features similar to pitting corrosion. From the viewpoint of average corrosion rate and penetration depth the effect of endgrain attack on the corrosion of 18Cr-10Ni austenitic stainless was investigated in simulated dissolver liquor under non-boiling conditions. The average corrosion rate of coupons was evaluated as a function of endgrain ratio to total surface area. In addition the effect of orientation with respect to the rolling direction was measured directly by observing the dimensional change of holes drilled into coupons. It was found that the proportion of exposed endgrain affected the coupon corrosion rate. From the hole growth measurements it was found that the average corrosion rate in the rolling direction was 2.3 mm/yr approximately 1.5 times higher than that of the vertical one on the surface. From sections the maximum extent of pitting penetration into the endgrain was estimated to be approximately 8.8 mm/yr. © 2004 Taylor & Francis Group, LLC.