Adsorption and passivation behavior of copper alloy by phthalocyanine complexes in an aqueous chloride solution

The adsorption and protective properties of teraphthal, the sodium salt of 4.5-octacarboxyphthalocyanine, on the surface of the copper alloy MNZh5-1 in a neutral borate buffer solution were studied. Teraphthal suppresses active anodic dissolution of the MNZh5-1 alloy in 0.01 M chloride buffer pH 7.40. The protective effect increases at Сinh = 1.2 µmol/l from 0.18 V to 0.35 V at 25 µmol/l. The adsorption energy (-Δ𝐺 0 𝑎, 𝑚𝑎𝑥) of teraphthal on the surface of the MNZh5-1 alloy at E = 0.0 V is 78.8 kJ/mol. This value indicates chemisorption of the inhibitor on the electrode surface, which occurs due to the oxygen atoms of carboxyl groups. The thickness of the adsorbed layer, determined by ellipsometry methods, is ≈ 0.3 nm, which indicates a flat arrangement of teraphthal on the surface.