Corrosion Behavior of Carbon Steel in Synthetically Produced Oil Field Seawater

Abstract

The life of offshore steel structure in the oil production units is decided by the huge corrosive degradation due to SO42-, S2−, and Cl−, which normally present in the oil field seawater. Variation in pH and temperature further adds to the rate of degradation on steel. Corrosion behavior of mild steel is investigated through polarization, EIS, XRD, and optical and SEM microscopy. The effect of all 3 species is huge material degradation with FeSx and FeCl3 and their complex as corrosion products. EIS data match the model of Randle circuit with Warburg resistance. Addition of more corrosion species decreases impedance and increases capacitance values of the Randle circuit at the interface. The attack is found to be at the grain boundary as well as grain body with very prominent sulphide corrosion crack.

The effect of environmental variables on early corrosion of high–strength low–alloy mooring steel immersed in seawater

“…Generally, for all S, the corrosion rate (CR) increased with increasing temperature. This is in line with the model of corrosion rate controlled by chemical reactions and oxygen diffusion (Melchers's phases 0 and 1) [61]. In addition, it was found that the CR at non-standard salinity levels was considerably higher, than at S 35.…”