Inhibitor protection of copper in citric acid solutions

• Ya.G. Avdeev¹, K.L. Anfilov², E.P. Rukhlenko² and Yu.I. Kuznetsov¹

¹ A.N. Frumkin Institute of Physical Chemistry and Electrochemistry, Russian Academy of Sciences, Leninskii pr. 31, 119071 Moscow, Russian Federation
² Bauman Moscow State Technical University (Kaluga Branch), Bazhenov str. 2, 248000 Kaluga, Russian Federation

Abstract: The kinetics of copper corrosion and the effect of convection on this process were studied in freely aerated citric acid (C₆H₈O₇) solutions. The copper corrosion rate in this medium does not depend significantly on the duration of contact between copper and the corrosive medium (1–20 days) and C₆H₈O₇ concentration (0.001–2 M). The corrosivity of this medium towards copper increases with the transition from static to dynamic conditions of the experiment. Also, the corrosivity of C₆H₈O₇ solutions toward metallic copper is enhanced in the presence of the corrosion product, Cu(II) cations. This effect is especially pronounced when it comes into contact with a dynamic corrosive medium. A triazole derivative, IFKhAN-92, is recommended for copper protection in freely aerated C₆H₈O₇ solutions. The efficiency of this compound does not depend considerably on the duration of contact between the metal and the corrosive medium, C₆H₈O₇ content, and hydrodynamic characteristics of the solution. An important feature of the IFKhAN-92 inhibitor is that its protective ability toward metallic copper is preserved even if Cu(II) cations are accumulated in the corrosive medium, which is true not only in static but also in dynamic media. The dependence of the copper corrosion rate on the convective factor in freely aerated solution 2 M C₆H₈O₇+0.05 M Cu(II), both in the absence and in the presence of the corrosion inhibitor, is formally described by the equation k=a+b·n^1/2, where a and b are empirical parameters and n is the rotation frequency of the magnetic stirrer. The addition of IFKhAN-92 decreases the parameters a and b in this equation.

Keywords: corrosion, corrosion inhibitors, copper, citric acid, copper(II) cations, triazole

Int. J. Corros. Scale Inhib., 2021, 10, no. 3, 911-923
doi: 10.17675/2305-6894-2021-10-3-5

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