Corrosion damage and electrochemical corrosion behaviour of 8Cr4Mo4V bearing steel in a simulated marine-contaminated atmosphere

Abstract

The present work aims to explore corrosion damage evolution characteristics of 8Cr4Mo4V bearing steels in marine contaminated atmospheric conditions, considering effects of corrosion temperature, corrosion medium, medium concentration and rust layer. Salt spray tests and electrochemical techniques were conducted to evaluate the corrosion resistance and electrochemical corrosion property of 8Cr4Mo4V bearing steels, respectively. The corrosion kinetics, corrosion morphology, corrosion product composition, corrosion voltage, corrosion current density, impedance mode and polarisation resistance of samples were characterised by weight gain method, SEM, XRD and electrochemical tests. Results show that the corrosion damage degree of bearing steel in a simulated marine-industrial atmosphere is more serious compared with a marine atmosphere; the multi-layer composite rust layer is mainly iron oxides and hydroxyl oxides, accompanied by the formation of micro-cracks. The increased corrosion temperature, NaCl concentration, HSO₃⁻ concentration and NH₄⁺ concentration cause obvious fluctuations of electrochemical parameters and polarisation resistance of bearing steels, while the electrochemical impedance behaviour of corroded bearing steels changes in reverse due to the generation of rust layers, acting as a protector of the substrate material. These investigation findings prominently contribute to evaluating the accelerated corrosion behaviour and describing corrosion defect evolution of 8Cr4Mo4V bearing steels in a marine-contaminated atmosphere.