Effect of tempering heat treatment on the CO2 corrosion resistance of quench-hardened Cr-Mo low-alloy steels for oil and gas applications

Abstract

The corrosion resistances of a number of tempered states of two Cr-Mo low-alloy steels, the novel "HT10″ (martensitic) and the commercial ASTM A182 grade "F22″ (bainitic), were evaluated in CO2-saturated brine. The tempering heat treatments soften both steels, due to a decrease in dislocation density, and the precipitation of alloy carbides, but also decrease their uniform corrosion rates. Such a decrease is considerable if the steels are tempered at higher temperature for longer time. For the novel HT10, we discuss how the tempering-induced changes to the microstructure contribute to decreasing the cathodic reaction kinetics, and thus the general corrosion rate.