Protective structures on carbon steel in aqueous-salt solutions containing catholyte

Abstract

The process fluid of oil fields, with a huge amount of dissolved gases, mechanical impurities, salt ions, mineral acids and bases present in them, has a destructive effect on the internal surface of oil collection equipment. The simultaneous presence of carbon dioxide and hydrogen sulfide pose the greatest danger, since they are catalysts for the cathode reaction of hydrogen depolarization of low-alloy steel, and lead to the formation of soluble corrosion products - iron hydrogencarbonate. One common way to prevent electrochemical corrosion of oil equipment is to neutralize acidic components of process media. Sodium hydroxide is often used as a neutralizer, however, the content of sodium salts contaminates the obtained oil products and catalysts and leads to disruption of the technological process of its further processing. Accordingly, there is provided a process for the non-reactive neutralization of acidic components by introducing a solution of a hydroxide-saturated catholyte. In the scientific and technical literature, the problem of forming protective films on the surface of carbon steel by introducing catholyte into the process liquid remains insufficiently studied. In scientific research work, a method of forming surface structures by selecting the concentration of a catholyte solution has been developed. The thickness of the obtained protective structures obtained in the model of produced water formed on the surface of low-alloy steel A516-55 in solutions of sodium hydroxide and catholyte was calculated. The study revealed the dependence of the corrosion rate of steel on the concentration of sodium hydroxide solution and catholyte solution at various pH values.