Research on the Pitting Mechanism of Dispersion-Strengthened High-Strength Steel Under Wet-Dry Cycling in a Marine Environment

Due to the wet-dry cycling in the ocean tidal zone,the supply of dissolved oxygen and salt-containing particles were sufficient,so the corrosion was serious.Pitting corrosion was a common form of localized corrosion.This paper studied the pitting corrosion mechanism of dispersion-strengthened high-strength steel under different wet-dry ratio environments.Electrochemical Impedance Spectroscopy was used to study the changes of corrosion rate and electric double layer structure of the dispersionstrengthened high-strength steel.Scanning electron microscope,Raman spectroscopy,electron probe microanalysis and laser confocal scanning microscope were used to observe the corrosion product morphologies,analyze the corrosion product compositions,analyze the secondary distribution of alloy elements in the corrosion products and analyze the pitting information of the steel after the corrosion products were removed.The results showed that the degree of the steel corrosion was slight when the wetting time was longer,the size and depth of the corrosion pits on the surface were smaller.This was because the environment with longer wetting time made the corrosion products denser.In this environment,the conversion ofγ-FeOOH to Fe3O4 was promoted.In addition,it could also promote the alloying elements to be more concentrated in the rust layer.The above phenomena hindered the further corrosion of the matrix by dissolved oxygen and Cl−in the seawater.