The behaviour of praseodymium 4-hydroxycinnamate as an inhibitor for carbon dioxide corrosion and oxygen corrosion of steel in NaCl solutions

•Praseodymium 4-hydroxycinnamate (Pr(4OHCin)3) highly effective corrosion inhibitor.•Mechanism of inhibition different in CO2-saturated solutions compared to aerated system.•In natural aerated solutions a continuous protective film forms on the steel surface.•In CO2-saturated solutions inhibiting deposits form at active corrosion sites.

Praseodymium 4-hydroxycinnamate (Pr(4OHCin)3) was investigated as a novel corrosion inhibitor for steel in NaCl solutions, and found to be effective at inhibiting corrosion in both CO2-containing and naturally-aerated systems. Surface analysis results suggest that the corrosion inhibition ability of Pr(4OHCin)3 in the naturally-aerated corrosion system could be attributed to the formation of a continuous protective film. For the CO2-containing system, the corrosion inhibition efficiency of Pr(4OHCin)3 was predominantly because of formation of protective inhibiting deposits at the active electrochemical corrosion sites, in addition to a thinner surface film deposit.