Study on corrosion resistance mechanism of Cr-containing steel in simulated oilfield produced fluid

Abstract

In view of the CO2 corrosion environment of oil and gas fields, the corrosion behavior of 5Cr, 9Cr and 13Cr steels was studied by high temperature and high pressure weight loss test and electrochemical test with J55 material as comparison. Scanning electron microscopy (SEM) analysed the morphology of corrosion products. The corrosion resistance mechanism of Cr-containing steel was analyzed from the perspective of structural stability by first-principles. The results show that the uniform corrosion rate of Cr-containing alloy steel is lower than that of J55 steel, and the CO2 corrosion resistance of the material increases with the increase of Cr content. With the increase of temperature, the self-corrosion current density of different Cr-containing steels gradually increases, the pitting potential of 9Cr and 13Cr gradually decreases, and the pitting resistance decreases. The electrochemical corrosion kinetic resistance of Cr-containing steel increases under long-term immersion corrosion. Molecular dynamics and first-principles calculations show that the corrosion product preferentially formed by Fe is FeCO3, and the corrosion product preferentially formed by Cr is Cr(OH)3. On the surface of the iron matrix, Cr(OH)3 is more easily adsorbed on the surface of the iron matrix, thereby protecting the matrix from corrosion resistance.