Effects of LaAlO3 and La2O2S inclusions on the initialization of localized corrosion of pipeline steels in NaCl solution

Galvanic coupling theory is traditionally adopted to explain initialization of localized dissolution; however, in present study, the conductivity of LaAlO3 and La2O2S inclusions was calculated using first-principles to predict whether galvanic corrosion occurs or not. Further, influences of these inclusions on localized corrosion were examined by scanning electron microscope, energy dispersive spectrometer, electron back scattered diffraction, and immersion experiments. It was found that no galvanic coupling occurred between LaAlO3 and the matrix, and microcrevices are the main responsible for localized corrosion. Except microcrevices, an intrinsic potential difference between La2O2S and the matrix also contributes to the initialization of localized corrosion. [Display omitted]