<p>The inhibition efficiency of molybdate ions (MoO₄^2-) against tin corrosion in 0.2 M Malic acid has been studied using electrochemical (DC and AC) and surface analytical methods (SEM and EDX). The electrochemical polarization curves revealed the presence of an active/passive transition of the tin electrode. The electrochemical impedance measurements (EIS) confirmed the benefic effect of increasing MoO₄^2- concentration on the inhibition efficiency (η %) (reaching η_max≈ 88% at 0.02 M), whereas η % decreases by increasing temperature. The molybdate ions inhibition mechanism was attributed to the adsorption on the metal surface involving the formation of the adsorbed protective layer.<strong></strong></p>

The corrosion behaviour of pure tin in an aqueous solution simultaneously containing Cl -and SO4 2-ions has been studied using electrochemical techniques, optical and scanning electron microscopy. Measurements were conducted under different chloride and sulphate ions concentrations. The potentiodynamic polarisation curves showed that the pitting potential, Epit, is independent from the variation of pH, temperature and chloride and sulphate concentration of the solution. In its turn, an increase of these parameters stimulates shifting of corrosion potential to more active values and leads to an increase of the corrosion and passive current densities. The electrochemical features were strongly supported by optical and scanning electron micrographs of the corroded surfaces of the pure tin samples after potentiodynamic polarisation experiments and immersion tests.

The inhibition efficiency of H2PO42− ions against tin corrosion in 0.2 M maleic acid is studied using electrochemical methods, surface analytical methods, and thermodynamic analysis. The potentiodynamic polarization plots showed the presence of an active/passive transition state of the tin electrode. The EIS measurements confirmed that the inhibition efficiency of H2PO42− increased by increasing the concentration (η=81 % at Cinh=2.10−2 M) and decreased by rising the temperature. The polarization tests demonstrated that the inhibitor performs as a cathodic‐type. The adsorption of the inhibitor was spontaneous and followed the Langmuir adsorption isotherm. A model of the inhibition mechanism was suggested.

The influence of hydrogen phosphate (HPO42−) and molybdate ions (MoO42−) on the behavior of tin corrosion in 0.2 M maleic acid was compared using experimental and theoretical techniques. The experimental studies consisted of the electrochemical investigations (potentiodynamic polarization (PDP) and electrochemical impedance spectroscopy (EIS)), along with the surface analytical techniques (SEM and EDX). Additionally, the theoretical analysis (the chemical quantum computations at MP4/SDD level of theory in the aqueous phase), was conducted. The experimental outcomes illustrated that the inhibition efficiency (η%) increases with the concentration of the inhibitors, reaching 88 % and 81 % at 2×10−2 M concentration of MoO42− and HPO42−, respectively. The potentiodynamic polarization curves revealed that HPO42− performance is a cathodic‐type inhibitor, while MoO42− shows a mixed‐type behavior. The increase in temperature decreased the η% values of both inhibitors. Based on surface analysis and thermodynamic study, the presence of the two inhibitors formed protective films on the tin surface through a physisorption mechanism. The chemical quantum computations using the complete fourth‐order Møller Plesset perturbation theory (MP4 with SDD basis) method results outlined the favorable affinity of the investigated inorganic inhibitors to interact with the tin surface, which interprets the well‐observed inhibition efficiencies.

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