Laboratory Evaluation of Galvanic CO2 Corrosion and Inhibition of Carbon Steel Piping Partially Clad with Alloy 625

Polarization, galvanic current and immersion tests were conducted to evaluate galvanic corrosion and preferential weld corrosion of carbon steel coupled to Alloy 625 in CO2-saturated brine at 66 C. Three inhibitors were evaluated for their ability to reduce galvanic corrosion at concentration of 150 ppm v/v.  Galvanic coupling with an area ratio 1:1 was shown to double the uncoupled uninhibited CO₂ corrosion rate.  All of the inhibitors evaluated were shown to be efficient in mitigating uncoupled uniform corrosion, but only one was able to also reduce galvanic currents to negligible values while showing no evidence of preferential weld corrosion or pitting.