Synergistic effect of oxide film and MTZ: achieving optimal corrosion inhibition efficiency for L245 carbon steel in CO2–O2 coexisting environments

Purpose The purpose of this study is to address the severe corrosion of L245 carbon steel in CO2-O2 coexistence environments within oil and gas fields. Therefore, a strategy involving the formation of a dual-layer film (oxide film + inhibitor film) on the L245 carbon steel surface is proposed. Design/methodology/approach A double-layer film with an outer hydrogen barrier layer and an inner oxygen-resistant layer [oxide film/3-mercapto-1,2,4-triazole (MTZ) corrosion inhibitor] was designed. The weight loss method, electrochemical tests, surface morphology analysis and molecular dynamics simulation were adopted to evaluate its performance in a 2 Wt.% sodium chloride solution, and the underlying mechanism was investigated. Findings The double-layer film showed excellent protective performance in CO2–O2 coexisting environment. Molecular dynamics simulation verified that MTZ inhibitor had stronger adsorption affinity on iron oxide than on iron. Originality/value The double-layer film composed of the inner oxide film and the outer MTZ corrosion inhibitor film can achieve the dual effects of blocking H + and resisting O2.