Electrochemical studies on the inhibition behavior of copper corrosion in pickling acid using quaternary ammonium salts

The inhibition effect of two quaternary ammonium salts namely: N¹,N²-didodecyl-N¹,N¹,N²,N²-tetramethylethane-1,2-diaminium bromide (I) and N-(2-hydroxyethyl)-N,N-dimethyldodecan-1-aminium bromide (II) on the corrosion of copper in 1 M HNO₃ has been investigated by polarization, electrochemical impedance spectroscopy (EIS) and electrochemical frequency modulation (EFM) techniques. Polarization studies showed that these compounds are mixed-type inhibitors. The inhibition efficiency increases with increasing the inhibitor concentration and the maximum inhibition (93.9% and 90.8%) was obtained in the presence of 1 × 10^{- 3} M of I and II, respectively. The adsorption of these inhibitors on the copper surface obeys Langmuir isotherm. The results obtained from the different electrochemical techniques were in good agreement.