Corrosion Behavior of X65 Steel in Simulated Environments for Submarine Pipeline During Storage

The corrosion behavior of X65 steel in seawater and freshwater and the addition of different kinds of deoxidizers and corrosion inhibitors was analyzed by polarization curve, macro corrosion morphology, micro corrosion morphology, corrosion rate and three-dimensional pitting morphology. The results showed that the maximum positive shift of self-corrosion potential of X65 steel was 11.6 mV after adding corrosion inhibitor in seawater, and the maximum positive shift of self-corrosion potential was 51.5 mV after further adding deoxidizer. With the extension of immersion time, a denser corrosion product film grew on surface of the sample, and the maximum pitting rate decreased from 0.881 2 mm/a to 0.680 4 mm/a, which played a protective role on surface of the sample. After adding deoxidizer and corrosion inhibitor in seawater, the maximum pitting corrosion rate of X65 steel decreased to 0.106 8 mm/a, which further confirmed that the synergistic effect of deoxidizer and corrosion inhibitor could effectively alleviate dissolved oxygen corrosion. It was recommended to add deoxidizer+corrosion inhibitor HYH-80-SEA in the storage process of X65 steel sea pipe. The corrosion rate of X65 steel in seawater was 10 times higher than that in freshwater at room temperature, while the corrosion rate of X65 steel in seawater was still 2-4 times higher than that in freshwater after adding deoxidizer and corrosion inhibitor HYH-80-SEA.