ISSN 2305-6894

Adsorption and passivation of a copper alloy by teraphthal in neutral chloride solution

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A.N. Frumkin Institute of Physical Chemistry and Electrochemistry, Russian Academy of Sciences, Leninskii pr. 31, 119071 Moscow, Russian Federation

Abstract: The adsorption and protective properties of teraphthal, the sodium salt of 4,5-octacarboxyphthalocyanine, on oxidized surface of copper–nickel alloy MNZh5-1 in a borate buffer solution have been studied. Teraphthal suppressed the active anodic dissolution of MNZh5-1 alloy in a neutral borate buffer with addition of 10 mmol/L NaCl. The protective effect is ΔE=0.35 V at Сinh=25 µmol/L. The adsorption isotherm of teraphthal on the oxidized surface of MNZh5-1 alloy was calculated using the full Temkin isotherm. The value of the standard free energy of adsorption –ΔGa0=78.8 kJ/mol suggests the chemisorption interaction of these organic anions with the oxidized surface of the alloy. XPS studies of the surface layers of the alloy after soaking in a teraphthal solution showed that it is strongly adsorbed on the oxidized electrode surface mainly coated with Cu2O. Binding of teraphthal to the alloy surface occurs due to oxygen atoms of carboxyl groups. The thicknesses of the adsorbed layer determined by ellipsometry and XPS coincide and amount to ~0.3 nm. This thickness indicates a flat arrangement of the teraphtal anion on the surface.

Keywords: copper alloy, sodium salt of 4,5-octacarboxyphthalocyanine, adsorption, neutral chloride solution, ellipsometry, Temkin isotherm, XPS, monolayer thickness

Int. J. Corros. Scale Inhib., , 11, no. 4, 1787-1801
doi: 10.17675/2305-6894-2022-11-4-24

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