Corrosion inhibition of copper in HNO3 solution using thiophene and its derivatives

The corrosion behavior of copper in the presence of thiophene (T) and some of its derivatives [2-thiophene carboxylic acid (TC) and 2-thienyl ethanol (TE)] has been investigated in 2 M HNO3 solution using electrochemical frequency modulation (EFM), electrochemical impedance spectroscopy (EIS), potentiodynamic polarization and weight loss techniques. Polarization studies showed that these compounds act as mixed type inhibitors. EFM technique provides a new tool for electrochemical corrosion monitoring and was used as an effective method for corrosion rate determination. In EFM measurements corrosion current density was determined without prior knowledge of Tafel slopes. Inhibition efficiency of these compounds has been found to vary with concentrations of the compounds and temperature. The adsorption of these compounds on the copper surface from the acid solution has been found to obey Langmuir adsorption isotherm. The thermodynamic activation parameters of copper corrosion in 2 M HNO3 were determined and discussed. The results obtained from EFM, EIS, Tafel and weight loss measurements were in good agreement.