The Electrochemical Characterization Of High-strength Steel During Corrosion Fatigue Crack Propagation

Corrosion fatigue is the fracture behavior of structures under the combined actions of fluctuating loads and corrosive environment. Corrosion fatigue damage is one of the main failure modes for naval architecture and ocean structures and has been a vital research field for a long time in ship building and ocean engineering. The available data show: Corrosion fatigue is the most encountered corrosion damage accident, accounting for nearly 30% of the total number of the accidents. It is obvious that corrosion fatigue is very universal and dangerous.With respect to the typical marine material/ agent system of high-strength steel/ NaCl solution, the present paper carries out the following work: (1) Electrochemistry of corrosion fatigue of high-strength steel. (2) The model of polarization potention- corrosion fatigue crack propagation. (3) The corrosion fatigue mechanism of high-strength steel.(1) The corrosion fatigue crack zone potential and other electrochemistry parameter are studied with the polarization curve, electrochemical impedance technique in the whole process of corrosion fatigue crack propagation of high-strength steel. And the relationship model between electrode potential E and corrosion fatigue crack propagation rate of high-strength steel is established.(2) The variation law of corrosion fatigue crack propagation and corrosion fatigue life N of high-strength steel with polarization potention is studied. The polarization potential range is identified when high-strength steel have higher corrosion fatigue life N. The relationship model between polarization potential E and corrosion fatigue crack propagation rate of high-strength steel is established. The results show that is strong cathodic polarization and anodic polarization can increase the corrosion fatigue crack propagation rate and reduce the corrosion fatigue life of the high-strength steel. The high-strength steel have a higer corrosion fatigue life when the polarization potential is -1000mV, so -1000mV is optimum protection potential.(3)The influence of polarization potention on corrosion fatigue crack propagation mechanism is studied by monitoring the electric current and observing fracture morphology. And the results show that under the conditions of anodic the corrosion fatigue crack propagation is mainly influenced by anodic dissolution and hydrogen embrittlement is the leading crack propagation mechanism at the cathodic polarization potention.