Stress Corrosion Cracking of Austenitic Cast Irons in Seawater and Brine, and Its Prevention

Stress corrosion cracking (SCC) behavior of austenitic cast irons, ASTM A436 Type 2 and A439 Type D2, hereafter referred to as Types 2 and D2 respectively, in NaCl solutions was studied. Initially, constant tensile load tests were conducted for the SCC experiment using smooth round-bar specimens to examine influences of applied stress, alloying elements, temperature, NaCl concentration, dissolved oxygen (DO) concentration, and potential on SCC behavior. Protection methods against SCC are discussed based on the test results. It was found that in an aerated NaCl solution, austenitic cast irons show a high SCC susceptibility, which is higher in Type 2 than in Type D2. The SCC mechanism is confirmed to be of the active path corrosion cracking (APCC) type; therefore, cathodic protection (CP) is the most effective way to prevent SCC. Furthermore, it was found that a reduction in stress, an increase in Ni content, and a decrease in DO concentration of the solution are also effective ways to prevent SCC.