Corrosion Failure Analysis of Nickel-Plated Tubing in CO2-Ca2+-SRB Environment of Offshore Oil Fields.

Corrosion failure of oil well tubing in the ocean can lead to significant economic losses. Surface treatment is often used to enhance the corrosion resistance of tubing, while corrosion acceleration will occur in a certain environment. This work combined onset failure analysis and corrosion simulation measurements to understand the failure procedure and corrosion mechanism of nickel plating materials in calcium chloride water-type weak corrosion environment. The microscopic analysis results of the failed part show CO2 corrosion products co-deposit with SRB bacterial sulfide products and Ca compounds. The damage of nickel plating is accompanied by S-containing products, which was confirmed by simulated immersion experiments at 50 °C, 0.28 MPa CO2 partial pressure, and a speed of 3 m/s. The aggressive solution penetrates through the micro-damage pores, followed by the degradation of the Ni plating layer into NiS, leading to the localized loss of protection and triggering under-deposit corrosion. Concurrently, the SRB's anaerobic environment generates CO2 corrosion byproducts and SRB-derived FeS.