Acrylonitrile derivatives as corrosion inhibitors for Cu10Ni alloy in 0.5 M hydrochloric acid solution

Corrosion inhibition of Cu10Ni alloy in 0.5 M HCl solution using acrylonitrile derivatives namely: (E)-2-(1H-indole-3-carbonyl)-3-(2-oxo-2-phenylethylthio)-3-(phenylamino)acrylonitrile(a),(E)-2-(1H-indole-3-carbonyl)-3-mercapto-3-(phenylamino)acrylonitrile(b)and(Z)-2-(1H-indole-3-carbonyl)-3 phenylacrylonitrile (c) was investigated by potentiodynamic polarization, electrochemical impedance spectroscopy (EIS) and electrochemical frequency modulation (EFM). Effect of temperature on the efficiency of the corrosion inhibition process was studied and the values of thermodynamic activation parameters were calculated and discussed. The inhibition was found to increase with increasing inhibitor concentrations and decreases with increasing temperature. Polarization data indicate that the examined acrylonitrile derivatives act as mixed type (cathodic/anodic) inhibitors. EIS results show that the change in impedance parameters with the concentration of the acrylonitrile derivatives studied is indicative of the adsorption of acrylonitrile derivatives molecules on Cu10Ni alloy surface. The adsorption of investigated compounds on Cu10Ni alloy surface has been found to obey Langmuir adsorption isotherm.     Key words: Corrosion inhibition, hydrochloric acid (HCl), Cu10Ni alloy, acrylonitrile derivatives.