Volume 23, Issue 1 (January 1995)
Assessment of the Corrosion Behavior of SS 304L in Nitric Acid Environments—An Alternative Approach
Stainless steel (SS) 304L is widely used as a construction material in industries requiring corrosion resistance in nitric acid environments. Representative samples from 20 heats of SS 304L products were subjected to a testing procedure consisting of testing as per the rapid screening test (Practice A) and the Huey test (Practice C) of ASTM A 262, Practices for Detecting Susceptibility to Intergranular Attack in Austenitic Stainless Steels. The presensitization heat treatment of 677°C for 1 h and the modified heat treatment of 677°C for 20 min were used for characterizing the microstructures in Practice A, whereas only the former presensitization heat treatment was used for Practice C. The percent duality after the two heat treatments has been correlated with the corrosion rate obtained in Practice C. A chemical composition based parameter, Cr effective = [% Cr − 0.18 (%Ni) − 100 (%C)], was calculated for all the heats and correlated with the percent duality after the two heat treatments as well as the corrosion rate in Practice C. It is observed that the SS 304L heats with Cr effective >14.0 and <50% grain boundary coverage after the modified heat treatment (Practice A) show low corrosion rates in Practice C. This eliminates the need for carrying out the lengthy Practice C of ASTM. Examples of heats of SS 304L are given to show that the modified presensitization heat treatment has better efficiency in screening materials and also exhibited better correlation with the results obtained in the Practice C. Guide rules for selection of SS 304L heats for nitric acid service are also suggested. Erratum to this paper appears in 23(2).