Abstract
The field experience in H2S + CO2 corrosion which was first reported in 20061 has been significantly increased, some of which has been made available in the literature. Several new cases are included in this paper. This experience has been compiled and extensively analyzed during the last few years, which has allowed some recurrent corrosion effects to be found, and some lessons learned on how to address or mitigate such effects. Six distinct recurrent findings are listed in this paper.
These findings have been analyzed in a very simple approach, which can be summarized as follows:
? Under significantly sour conditions and despite a permanent contact with water, the H2S + CO2 carbon steel corrosion rate typically remains low, as long as the following conditions are met:
1. There are sufficient anions and cations at the steel surface to ensure quick FeS precipitation at the steel-water interface,
2. Precipitation kinetics are high enough to ensure the precipitation reaction to be immediate at the interface, hence producing a dense protective corrosion product layer,
3. No detrimental factor is present that would alter this protective layer, neither locally nor on extended parts of the surface.
? On the other hand, H2S + CO2 corrosion of carbon steel is possible, as long as water is present, if any of these 3 conditions is not fulfilled.
Though this summary does not provide a detailed mechanistic description of H2S + CO2 corrosion, it provides a very simple way to approach this corrosion threat, while also showing essential tendencies and suggested barriers that future mechanistic description should be able to explain.
