The petroleum and chemical industries contain a wide variety of corrosive environments, many of which are unique to these industries. Oil and gas production operations consume a tremendous amount of iron and steel pipe, tubing, pumps, valves, and sucker rods. Metallic corrosion is costly.
By selecting the correct material and applying proper corrosion protection methods, costs can be reduced. This book provides design requirements to prevent or control corrosion damage safely and economically. 3rd edition 2014 Wiley
Residual elements (RE) in carbon steel, not specifically included in the specified steel, appear to influence the corrosion rate under certain conditions, especially in services involving hydrofluoric acid (HF). The relative proportions of RE, specifically %C, %Ni, %Cu, and %Cr in carbon steel base and weld metals used in refineries, especially in alkylation processes with HF as the catalyst, significantly impact corrosion behavior. Studies described in the literature show corrosion damage with high RE (Cu + Ni + Cr >0.20) components as compared to low RE (Cu + Ni + Cr <0.20) components.
In this study, electrochemical corrosion testing was performed on a 3-inch pipe elbow section with high REs that had developed a through-wall leak in service. Test results were compared to those obtained on a similar pipe elbow section with lower REs. The samples were exposed to 50% HF at room temperature and at 65°C. Linear polarization resistance (LPR) corrosion rates were measured at both temperatures. Potentiodynamic (PD) polarization scans were performed on samples of low and high RE steel exposed to 50% HF at room temperature.
Test results indicated that LPR corrosion rates were higher for the high RE carbon steel samples than for low RE carbon steel samples at both temperatures. PD scans showed that the critical current densities were higher for high RE steel than for low RE steel.