1992 Volume 41 Issue 1 Pages 10-18
The corrosion resistance of austenitic stainless steels was affected by Cr content and the impurity segregation at grain boundary in highly oxidizing nitric acid solution. In this study, effects of Cr (9-32%) and P (0.0002-0.034%) on the corrosion resistance of austenitic stainless steels were investigated in hot 8N nitric acid solution containing Cr6+ (0-1.0g/l). The main results are as follows: (1) The corrosion resistance in pure HNO3 was improved with the increase of Cr content. Cr oxide film was effective in pure HNO3. (2) The corrosion rate for (8-20) Cr-11Ni steels in 8N HNO3 containing Cr6+ more than 0.05g/l was increased with the increase of Cr content. This tendency on corrosion rate with Cr content was caused by the suppression of the cathodic reaction with the decrease of Cr content. (3) The corrosion rate of the austenitic stainless steels with more than 20% Ni was improved with Cr even in HNO3 containing Cr6+. (4) P less than 0.034% did not affect the corrosion resistance of the solution heat treated stainless steels. When stainless steels were sensitized at 650°C for short time, P less than 0.015% did not affect the intergranular corrosion depth. (5) The intergranular corrosion due to P segregation indicated the maximum value, when the stainless steel was sensitized at 650°C.
