The effects of micro-alloying of plain carbon steel with Cr and Mo on the corrosion behavior in CO2-saturated ( sweet) brine (0.5 M NaCl, pH 6.6) environment, under hydrodynamic conditions, at 80 degrees C were investigated. Crystalline siderite/chukanovite scales formed on all the alloys. Analysis of potentiostatic current transient data suggest that there exists a synergistic interaction between Cr and Mo, which induces more rapid crystallization of the scale compared to Mo-free steels. Increasing the Mo content also suppressed the transport-dependent dissolution current passing through the initially-present amorphous surface film. TEM images of the FIB-sectioned corrosion scales confirm that the corrosion scale formed on 1Cr0.7Mo is comparatively thinner and yet offers greater protectiveness when compared to the plain carbon steel. (C) The Author(s) 2018. Published by ECS.