Measured corrosion rates of carbon, low alloy, and stainless steels are significantly higher than that predicted by the modified McConomy curves in cases where significant concentrations of mercaptans are present in crude oils and hydrocarbon condensates. It suggested that these organic sulfur containing hydrocarbons cause higher corrosion rates than sulfur species in general. The corrosivity of four different mercaptans and selected crude oil fractions were measured in laboratory tests. It was concluded that mercaptan corrosion can contribute significantly to the total sulfur related corrosion in the temperature range 235–300°C, which agrees with observations of elevated temperature corrosion in refinery distillation equipment. The consequences for refinery equipment are discussed for furnace piping and crude distillers.
Keywords: Mercaptan, sulfur, corrosion, sulfidation, McConomy curves, corrosivity, weight loss, coupon, corrosion test