Monitoring of corrosion-fatigue degradation of grade R4 steel using an electrochemical-mechanical combined approach

The study deals with degradation and failure of mooring chains by the combined effect of corrosion and mechanical cyclic stresses on steel. Monitoring of the corrosion-fatigue damage was carried out using electrochemical assessment during the application of the cyclic mechanical loading on grade R4 martensitic steel specimens, immersed in artificial seawater. The spontaneous potential of the steel specimens and Electrochemical Impedance Spectroscopy measurements were performed to assess the corrosion degradation. Tests conducted under fully reversed stress-controlled loading have shown earlier failure caused by the corrosive environment when compared with the tests performed in ambient air. The corrosion potential response was used to identify the crack initiation and propagation stages.