The Corrosion Characterization in Simulated Heat-Affected Zones of X80 Pipeline Steel in Near-Neutral Solution

The microstructure evolution and corrosion characterization under elastic stress in near-neutral chloride bearing solution of X80 pipeline steel simulated heat-affected zone (HAZ) were studied. It is shown that the corrosion resistance in fine grain HAZ (FGHAZ) is the best which can be attributed to the fine grains and the uniform distribution of M/A islands. In addition, the corrosion resistance of coarse grain HAZ (CGHAZ) with high peak temperature is the weakest which can be attributed to the coarse microstructure. In addition, relatively high heat input should be taken to improve the corrosion resistance in CGHAZ. It is found that four couples of galvanic effects exist at least which can promote the occurrence of localized corrosion. The presence of two obviously different parts in corrosion morphologies and the presence of pitting holes which locate in M/A islands sites on base material and CGHAZ surfaces can be attributed to the galvanic effects.