Ce-citrate as green corrosion inhibitor for low alloy steel and aluminium alloys

Abstract

The efficacy of the environmentally friendly corrosion inhibitor Ce-citrate (0.1-0.5 mM) was analyzed on AISI 4130 low alloy carbon steel and AA7075 aluminum alloy in 0.05 M NaCl solution. Measurements of resistance to general corrosion were performed by electrochemical impedance spectroscopy and potentiodynamic polarization test. Resistance to pitting corrosion is determined based on the value of pitting potential Epit. For comparison, corrosion resistance measurements and pitting potential determination, for considered alloys, were performed in Ce-chloride solution. Changes on the surface of the specimens after corrosion testing were analyzed by SEM microscopy. The XPS method was used for the analyses of the formed inhibitory layer on the steel specimen surface. It has been shown that significant amounts of cerium, as well as the citrate anions, are present in the inhibitory layer. Ce-citrates have proved to be an effective corrosion inhibitor for AISI 4130 steel as well as an effective pitting corrosion inhibitor for AA7075 aluminum alloy. The mechanism of action of Ce-citrate on AISI 4130 steel and AA7075 aluminum alloy has been proposed.