STUDY OF CORROSION RESISTANCE OF SURFACE STRUCTURES FORMING ON LOW-ALLOYED STEEL SURFACE IN THE PRESENCE OF CATHOLYTE

Abstract

The presence in the process fluid of oil fields of numerous corrosive agents, such as salt ions, dissolved gases, solids and microorganisms, provokes the destruction of oil and gas equipment. The greatest danger is acidic gases - carbon dioxide and hydrogen sulfide. Their simultaneous presence is especially dangerous. They are catalysts for the cathodic reaction of hydrogen depolarization of low alloy steel. In the presence of carbon dioxide and hydrogen sulfide, the formation of soluble corrosion products - iron bicarbonate - takes place. Therefore, one of the ways to prevent the development of electrochemical corrosion is the neutralization of acidic components of the process fluid. The main neutralizer in this case is a sodium hydroxide solution. However, the presence of sodium salts in oil can provoke a violation of the technological process of its further processing due to contamination of the resulting oil products and catalysts. In this regard, the development of a method for the non-reagent neutralization of acidic components of the technological environment of oil fields is an urgent task. The use of catholyte, a solution saturated with hydroxide ions, is proposed as a neutralizer of acidic components of the technological environment of oil fields. The research paper examined the principles of the formation of surface structures in the presence of catholyte. A comparative assessment of the corrosion resistance of iron hydroxide films in a reservoir water model obtained on low-alloy steel 09G2S in solutions of sodium hydroxide and catholyte is shown. The study made it possible to establish the effect of catholyte on the kinetics of corrosion, and also revealed the dependence of the corrosion rate of steel on the concentration of alkali and catholyte reagent at various pH values. Microscopic studies have shown that in the presence of catholyte a thinner (plastic) film is formed with high corrosion resistance and protective effect.