Study of the Effect of Oil Borehole Water-Salt Medium on Pipe Steel X60 Electrochemical Corrosion Resistance

Corrosion-electrochemical processes for pipe steel X60 in model solutions of the Usinsk deposit with different pH values are studied. In an acidic medium with (pH 2.10) the test steel corrosion rate is faster by more than a factor of 2.5 than in a medium with pH of 6.31. In the range of pH values 6.31–4.01 steel X60 corrosion rate changes insignificantly (1.88–1.95 g/(m2 ·h)). With an increase in pH from 2.10 to 6.31 steel X60 free corrosion potential moves into the region of negative values (from –0.307 to –0.416 V /n.h.e/) due to formation of sulfide porous films of complex composition fulfilling the function of cathodes in a corrosion microgalvanic element Fe–FexSy. Corrosion process cathodic and anodic reaction parameters are calculated from polarization curves. In an acid medium (pH < 4) liberation of hydrogen proceeds with a limiting stage, both as a slow discharge, and also as delayed recombination. The anodic process of steel dissolution is accomplished by a Bockris mechanism with formation of a catalytic complex Fe−H−SHads+\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ \mathrm{Fe}-{\left(\mathrm{H}-\mathrm{SH}\right)}_{\mathrm{ads}}^{+} $$\end{document} or Fe(HS−)ads.