Modeling galvanic corrosion of 316L/40Cr and Ni–P coated 42CrMo alloys in downhole produced water corrosion environment

Abstract Water originating from underground frequently leads to severe corrosion of subsurface equipment and tubing, increasing the risks of structural failure, pipeline leakage, and environmental contamination, which can endanger both operational safety and environmental integrity. To delve into the galvanic corrosion of downhole equipment and tubing, a comprehensive study was conducted using COMSOL simulations to explore the galvanic corrosion mechanism between 316L/40Cr and Ni–P coated 42CrMo alloys. According to the electrochemical tests, a two-dimensional galvanic corrosion model encompassing 316L/40Cr, Ni–P coating, and 42CrMo substrate was established. The mechanisms of galvanic corrosion under varying material and coating damage scenarios were extensively discussed and analyzed. The findings reveal that, when the Ni–P coating remains intact, 40Cr undergoes more pronounced corrosion (approximately 35.3 µ m) compared to 316L (about 2.11 µ m). However, upon coating damage, 316L becomes the cathode, while 40Cr and 42CrMo function as anodes. Notably, the total current in the coupled system (0.475 mA) comprising 316L, 42CrMo, and Ni–P coating is lower than that in the system (0.712 mA) with 40Cr, 42CrMo, and Ni–P coating. Additionally, an increase in the surface area of the 316L electrode correlates with an enhanced corrosion rate, manifesting in corrosion depths of 32.09–32.16 µ m, 31.3–31.2 µ m, and 30.172–30.312 µ m at 400, 300, and 200 µ m, respectively.