Abstract
The effect of hydrogen sulphide on the corrosion of a range of steels in solutions of sodium chloride, and also, separately, in ammonium chloride/hydrochloric acid solutions, has been studied. The following alloys were included in the study: 04J Armco iron, St3S carbon steel, 1H13 13Cr ferritic stainless steel, H17 17Cr ferritic stainless steel, 1H18N9T austenitic stainless steel 18Cr9NiTi, and H17N13M2T austenitic stainless steel 17Cr13Ni2MoTi. The measurements were taken in deaerated solutions saturated with H2S or with H2S in the presence of hydrocarbons (pharmaceutical gasoline) in the temperature range 10–70°C. It was found that none of the steels was resistant to corrosion in the solutions and temperatures investigated. This conclusion is valid specifically for alloy steels whose corrosion resistance results from the stable state of complete passivity. When the attainment of passivity is obstructed, as is the case in the presence of H2S, in the presence of chloride ions, and/or at higher temperatures or when the surface is scratched or cathodically reduced to expose bare metal, then even the austenitic stainless steels may be less corrosion resistant than ordinary carbon steel. A decrease in pH (in 2%NH4Cl and HCl solutions) leads to a further reduction in corrosion resistance. The presence of the hydrocarbon phase weakly hinders corrosion in the active state. The electrochemical parameters of the corrosion processes for the steels studied have been determined.
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