Dependence of corrosion resistance of structural pipe steels on the content of chromium and copper in oilfield calcium chloride media with different contents of aggressive ions

Abstract

In this work, we investigate specimens of rolled structural pipe steels of industrial smelting at NLMK PJSC and those of laboratory smelting with various alloying systems (C–Mn–Si, C–Mn–Si–Cr, C–Mn–Si–Cr–Cu, and C–Mn–Si–Cr–Ni–Cu) subjected to dynamic corrosion tests in circulating calcium-chloride environments with different contents of aggressive ions, typical of the Khanty-Mansiysk region. The laboratory-smelted specimens with a chromium content of 0.6% in the absence of corrosive nonmetallic inclusions in the metal exhibited the lowest corrosion rate. The corrosion film was established to consist of three layers, different in appearance, structure, and chemical composition. Only one of the layers, referred to as “gray” by its color, is characterized by increased Cr and Cu contents, thereby being promising for application in the studied corrosive conditions. A mutual positive effect of Cr and Cu additives on the corrosion resistance of structural steels, exposed to the aggressive environments typical of the Khanty-Mansiysk region, is established.