Corrosion of N80-Type Steel by CO2/Water Mixtures

The initial high corrosion rates of low-alloy carbon steel in CO2/brine mixtures are mitigated by the subsequent generation of loosely adherent iron carbide surface films, iron carbonate surface films, and, in the case of unbuffered waters, by a significant increase in pH caused by the loss of acid to the corrosion process forming these films. The actual time required to build up a passivating layer of siderite crystals on the steel surface is a function of the solution pH, via siderite solubility product considerations, and the ability of the corrosion scale particles to adhere to the steel surface.