Inhibition of anodic dissolution and corrosion of copper and its alloy in aqueous solutions by fuchsin

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

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

Abstract: The adsorption of acid fuchsin (AF) and its inhibiting properties toward the anodic dissolution and corrosion of copper alloy MNZh5-1 and its components (Cu, low-carbon steel St3, Ni) were studied in neutral and alkaline solutions. The adsorption of AF on the alloy and copper in a neutral medium proceeds better than in a weakly alkaline medium. On the oxidized surface of St3 in an environment with pH 9.2, adsorption occurs in the region of lower concentrations than at pH 7.4. The adsorption of AF in a neutral solution on Cu and MNZh5-1 alloy free from oxides is described by the complete Temkin equation with the free energy of adsorption (–Δ⁰_a,max)=47.2 and 80.2 kJ/mol, respectively. This is significantly higher than in a slightly alkaline environment where
(–Δ⁰_a,max)=37.3 and 55.8 kJ/mol, respectively. The orientation of AF on the oxidized surface of copper and the alloy is close to vertical. Corrosion tests of copper in 0.01 M NaCl solution showed that addition of 1.5 mmol/L AF completely suppressed copper corrosion. On the MNZh5-1 alloy under the same conditions, the degree of protection is Z=49.3%. In 3.5% NaCl solution at C_inh=
1.0 mmol/L, the degree of copper protection reaches 60.5%, while that of the alloy is 22%.

Keywords: St3 steel, copper, MNZh5-1 alloy, triphenylmethane dyes, acid fuchsin, passivity, adsorption, ellipsometry, free energy of adsorption

Int. J. Corros. Scale Inhib., 2024, 13, no. 1, 602-614
doi: 10.17675/2305-6894-2024-13-1-30

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