Application and evaluation of processing methods of electrochemical noise generated during stress corrosion cracking

Electrochemical noise generated during stress corrosion cracking (SCC) of t ype 304 stainless steel (UNS S30400) and a-brass were studied. Noise patter ns showed common characteristics (ie., a quick drop and slow recovery of th e potential). The quick drop corresponded to the initiation of localized ev ents where fresh metal was exposed. The slow recovery corresponded to the r epassivation process of the exposed bare metal. The potential drop rate and recovery rate were almost constant during the SCC process for a given SCC system. For random noise, rates of potential rise and drop were similar. Fr equency of the noise generated during SCC increased with an increase in app lied stress. SCC initiation could be monitored and determined according to noise characteristics and distribution. Since the shift of background poten tials had an obvious influence on characteristics of power spectrum density (PSD), the direct current (DC) component should be removed before analysis . Changes in standard deviation and PSD plateau with time could be used as criteria for monitoring SCC initiation.