Corrosion inhibition of steel in naturally-aerated chloride solution by rare-earth 4-hydroxycinnamate compound

•Gd(4OHCin)3 compound acts as a major corrosion inhibitor for steel in naturally-aerated chloride solution.•Gd(4OHCin)3 compound formed a protective film layer which acts as a barrier layer on the steel surface.•Gd(4OHCin)3 behaves as a mixed inhibitor but more predominantly as an anodic inhibitor.•Gd(4OHCin)3 compound produced higher resistance against localized attack.