Cerium citrate as ecologically friendly corrosion inhibitor for AA7075 alloy

The corrosion behaviour of high-strength AA7075 aluminium alloy in NaCl solution, without and in the presence of environmentally friendly corrosion inhibitors (Ce-chloride and Ce-citrate) in low concentrations (<0.5 mM), was analysed. The degree of precipitation of the solid solution of AA7075 alloy was determined by measuring the electrical conductivity, while the surface morphology and appearance of intermetallic compounds before and after corrosion testing were analysed by SEM/EDS method. The general corrosion resistance of the tested alloy in NaCl solution and the degree of the inhibitory effect of the corrosion inhibitors were determined on the basis of electrochemical impedance spectroscopy and polarization measurements, while resistance to pit formation on the bases of E-pit. AA7075 alloy showed high resistance to general corrosion in the presence of both tested inhibitors, while resistance to pit formation was significantly higher in the presence of Ce-citrate (concentration 0.5 mM). Also, Ce-citrate present in NaCl solution at lower concentrations provides satisfactory resistance of AA7075 alloy to general and pitting corrosion. A mechanism of protective action of Ce-citrate inhibitor has been proposed.