Corrosion fatigue and electrochemical reactions in modified HY130 steel

Abstract

To investigate the relationship between corrosion fatigue crack growth response of high strength steels in aqueous environments and electrochemical reactions at the crack tip, fatigue and electrochemical simulation tests were carried out on a modified HY130 steel in acetate buffer solution. Corrosion fatigue crack growth rates were determined as a function of temperature (276–363 K) and frequency (0.03–10 Hz) under open-circuit conditions. The electrochemical simulation experiments were carried out over the same range of temperatures and measured the galvanic current transient between a clean and an oxidized surface and the corresponding mixed potential. These experiments were based on the assumption that the newly created surfaces at the crack tip and its neighboring oxidized surfaces formed a localized galvanic cell. The results from the two sets of experiments strongly suggested electrochemical reaction control of corrosion fatigue crack growth. The electrochemical experiments indicated that hydrogen evolution in this system followed the Volmer-Heyrovsky mechanism. Because of uncertainties associated with extraneous charges introduced by cathodic cleaning of the clean surface, a definitive correlation and an identification of the rate-controlling process could not be made. The results and methods for alleviating this difficulty are discussed.