Influence of O₂ on Corrosion Resistance of Ultra-High Speed Laser Cladding 431M2 Coatings in CO₂ Aqueous Phase

O₂ impurities, as common impurities in CO₂ streams, can affect the corrosion resistance of pipeline materials during CO₂ oil drive. In order to understand the effect of O₂ impurities on stainless steel coatings containing defects at various stages of corrosion, this paper investigates the effect of O₂ on the corrosion resistance of ultra-high speed laser cladding 431M2 coatings in saturated CO₂ solution at pH3 using cyclic dynamic potential polarization, constant potential polarization tests and long cycle EIS tests. The results show that when the 431M2 coating is in the passivation zone, the presence of O₂ promotes the growth of the passive film and the coating protection performance is improved, but the sprouting of sub-steady state pitting becomes more. When the 431M2 coating is in steady-state pitting, the presence of O₂ promotes the development of local corrosion pits. Long-period EIS experiments show that O₂ impurities contribute to the growth of the coating passive film in the pre-corrosion stage, but with immersion time, once steady-state pitting occurs at the defect, O₂ impurities accelerate the occurrence of pitting and reduce the corrosion resistance of the coating.