Deuteroporphyrin as a copper surface modifier for its protection against corrosion in neutral solutions

• M.O. Agafonkina, N.P. Andreeva and Yu.I. Kuznetsov

Frumkin Institute of Physical Chemistry and Electrochemistry Russian Academy of Sciences, 31-4, Leninsky prospect, 119071 Moscow, Russian Federation

Abstract: The adsorption, protective and passivating action of deuteroporphyrin on copper in neutral buffer solutions has been studied. Deuteroporphyrin is adsorbed on the oxidized copper surface with the free energy of adsorption ΔG⁰_ads=45.1 kJ/mol calculated using the full Temkin isotherm. It has been shown that preliminary modification of oxidized copper with deuteroporphyrin enhances the adsorption of 5-chloro-1,2,3-benzotriazole (5-chloro-BTA) on it. The onset (start) of 5-chloro-BTA adsorption shifts by 2 orders of magnitude toward lower concentrations. The free energy of adsorption for 5-chloro-BTA on oxidized copper is 61.5 kJ/mol, while on the pre-adsorbed layer of deuteroporphyrin on copper it increases to 75.6 kJ/mol. If a monolayer of 5-chloro-BTA is applied to the surface, deuteroporphyrin adsorption doesn’t increase. The interaction of porphyrin with the metal substrate is weakened in the presence of an insulating layer, in this case a monolayer of 5-chloro-BTA. The orientation of deuteroporphyrin on the surface of oxidized copper is close (near) to horizontal. In a borate buffer pH 7.4+0.01 M NaCl, deuteroporphyrin stabilizes the passive state of copper at concentrations three orders of magnitude lower than the concentration of chloride ion. The combined (coactions) passivating and protective action of deuteroporphyrin and 5-chloro-BTA on copper is higher than that of individual compounds.

Keywords: adsorption, passivity, deuteroporphyrin, local depassivation potential, Temkin isotherm, free energy of adsorption, surface modification

Int. J. Corros. Scale Inhib., 2025, 14, no. 3, 1116-1129
doi: 10.17675/2305-6894-2025-14-3-6

Download PDF (Total downloads: 1)

Back to this issue content: 2025, Vol. 14, Issue 3 (pp. 1018-... (in progress))