The influence of 1000ppmm of acetic acid on the corrosion mechanisms of mild steel with up to 10 mbar (10000 ppmv) of H2S with and without CO2 at atmospheric pressure was investigated using electrochemical and surface analysis techniques. The results showed that anodic reaction retardation caused by acetic acid in CO2 corrosion at low temperatures was not observed when H2S was present in an H2S/CO2 environment. The potentiodynamic sweeps for H2S/CO2 corrosion showed a retardation of the corrosion rate which is thought to be caused by a thin mackinawite layer that is known to form in these conditions.
Trommer et al. (Tue,) studied this question.