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

The rare-earth organic compound Gadolinium 4-hydroxycinnamate (Gd(4OHCin)₃) was characterized and shown to be an effective corrosion inhibitor for mild steel in naturally-aerated 0.1 M chloride solution, not only of general corrosion but also of pitting corrosion. As the inhibition content increased, the corrosion inhibition efficiency increased, up to 94% at concentration of 0.93 mM inhibitor. The results also indicate that Gd(4OHCin)₃ behaves as a mixed inhibitor but more predominantly as an anodic inhibitor. The inhibition is attributed to the formation of a protective film layer which acts as a barrier layer on the steel surface. The infrared spectra also confirm a synergetic inhibition mechanism by rare earth and organic components of Gd (4OHCin)₃, which depends on inhibitor concentration and immersion time.