Abstract
Development of Preferential Corrosion of Weldment (PCW) was found in natural gas gathering lines in a sweet gas-condensate field. Effects of inhibition on these unique corrosion phenomena were studied. Effects of Cr and/or Mo addition to weld metal were also examined. At least 500 ppm of the inhibitor now in use is required to properly control the corrosion. The section of selective corrosion varied with inhibitor concentration. 0.5% addition of Mo effectively controls the selective localized corrosion of the weld metal. Although Cr is a beneficial alloying element to mitigate CO2 corrosion, 2%Cr-1%Mo weld metal selectively corrodes with concentration of the inhibitor 250 ppm. Galvanic effects on this preferential corrosion were not confirmed.
