The corrosion behavior of AA7049 aluminum alloy in NaCl solution in the presence of environmentally-friendly corrosion inhibitors (Ce-chloride, Ce-formate, Ce-acetate, and Ce-propionate) was analyzed. The chemical composition of intermetallic particles was evaluated by a Scanning Electron Microscope, equipped for Energy Dispersive Spectroscopy measurements, while the presence of cerium and type of functional groups in inhibitors surface layers were analyzed by X-ray Photoelectron Spectroscopy and Fourier-Transform Infrared Spectroscopy, respectively. Inhibitor efficiencies were tested by applying electrochemical techniques such as Electrochemical Impedance Spectroscopy and Linear Sweep Voltammetry. Ce-propionate showed a greater inhibitory effect than all other tested corrosion inhibitors. The inhibitory effect decreases in the following order: Ce-propionate > Ce-acetate > Ce-formate > Ce-chloride. Propionate anions have a higher water contact angle and also a longer aliphatic side chain than acetate and formate anions. The mechanism of inhibitory action of Ce-propionate and other tested corrosion inhibitors has been proposed.

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Green corrosion inhibitors, Ce(III) chloride, Ce(III) nitrate, and Ce(III) propionate, were tested in NaCl solution with the aim to evaluate their inhibitory effect on 7049 aluminum alloy and to propose a mechanism of their inhibitive action. Corrosion properties of the formed inhibitor layer were analyzed using electrochemical impedance spectroscopy, while the pit formation resistance was analyzed using potentiodynamic polarization tests. Morphology of the formed pits was evaluated by scanning electron microscope/energy‐dispersive spectroscopy analysis. It was shown that Ce(III) propionate in NaCl solution has a noticeably higher protective ability than Ce(III) chloride and Ce(III) nitrate. The presence of cerium, propionate anions, and Al–O bonds in the inhibitive layer on the 7049 aluminum alloy surface was confirmed by X‐ray photoelectron spectroscopy analysis. This indicates the formation of Ce propionate complexes and bonds via oxygen atoms from carboxylate anions with the metal surface. Density‐functional theory methods were used for the geometry optimization of possible Ce propionate complexes as corrosion inhibitors.

The new environmentally friendly corrosion inhibitor Ce-citrate was analyzed in 0.05 M NaCl solution on the AISI 4130 steel. For comparison, corrosion inhibitor Ce-chloride is tested in the same concentration as Ce-citrate (0.3 mM). Inhibitor efficiencies were determined by applying electrochemical impedance spectroscopy and potentiodynamic polarization measurements. The results of electrochemical measurements, the contact angle measurements, as well as the surface appearance of the specimens after the immersion in the inhibitive NaCl solution for 96 h confirmed that the new environmentally friendly inhibitor (Ce-citrate) has a significantly higher protective ability than the Ce-chloride. The protective ability of Ce-citrate increases over time, according to the proposed mechanism of its action. In the inhibitive layer formed in NaCl solution containing Ce-citrate, XPS analysis revealed the presence of cerium in oxidation states Ce III and Ce IV , citrate anions (carboxyl O-C═O group as well as C-OH and C-C and C-H bonds), oxide, hydroxide, and oxyhydroxide of iron (mainly FeOOH and Fe 2 O 3 ).The mechanism of inhibitory action of Ce-citrate was proposed and analyzed in detail.

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.