A study of crack initiation in corrosion-fatigue of AISI 316 stainless steel by dynamic measurement of corrosion characteristics and corrosion current transients
A technique has been developed and applied to monitor corrosion current transients, in phase with a cyclic stress. applied in reverse bending at 24 Ez to AISI 316 stainless steel plate immersed in selected aqueous media. The amplitude and waveform of this fluctuating current component, together with the measurement of the corrosion characteristics during fatigue, yield information on the nature of the stress-environment interaction. In conditions where the metal surface was passive, a mechanism is proposed, which involves the repeated transient depassivation of the surface at persistent slip bands, leaving ultimately to premature crack initiation. In conditions where the metal surface was active (transpassive) a mechanism is proposed, which involves the preferential dissolution at slip steps with resultant enhancement in plastic strain and premature crack initiation.