Straining metal electrodes AS a SCC test. Type 304 stainless steel in MgCI2, Ca CI2 and LicI solutions

Abstract

Straining metal electrode experiments are a valuable technique for predicting crack propagation rates and crack morphologies when anodic dissolution is the rate-determining step in stress corrosion cracking (SCC). The straining test provides the same information found through more conventional SCC tests, with the advantage of being considerably less time-consuming. In the present work this technique was applied to Type 304 stainless steel in MgCl 2, CaCl 2 and LiCl solutions, tested at room temperature and at 90° and 100°C. The predicted effects of temperature and electrode potential were in good agreement with those reported in the literature. A limit crack propagation rate from about 10 -8 to 10 -7 m s -1 was found, in agreement with values reported by other authors from fracture mechanic tests. Above the pitting potential the crack propagation rate was found to remain constant, but there was a sharp decrease in the bare metal/filmed metal current ratio, and SCC was replaced by generalized corrosion and pitting.