Mechanism of pitting corrosion induced by inclusions in Al-Ti-Mg deoxidized high strength pipeline steel.

ABSTRACT

In order to reveal the mechanism of galvanic pitting corrosion initiation induced by typical complex inclusions in Al-Ti-Mg deoxidized high strength pipeline steel, first-principles calculations, combining with immersion tests, scanning electron microscopy was used to study the correlation between electronic work function and galvanic corrosion of Al-Ti-Mg killed steel. The results show that MnS inclusions act as anodes in the electrochemical environment, preferentially corroding and dissolving; MgAl2O4 and Al2O3 inclusions act as cathodes, leading to the corrosion of Fe matrix; different end planes of MgTiO3 and MgTi2O4 act as both anodes and cathodes, but they have little effect on pitting corrosion. Microcrevices on the MgTiO3 and MgTi2O4 inclusions boundary are the main cause of matrix dissolution.