Abstract
Tert-butylhydroquinone (TBHQ) has been investigated as corrosion inhibitor for aluminum; copper and stainless steel in biodiesel blend B20 by using electrochemical impedance spectroscopy (EIS) method. The results showed that the inhibition efficiency increases with an increase in the concentration of TBHQ but decreases with increasing temperature from 30℃ to 60℃. A maximum inhibition efficiency of about 61.52% for aluminum was recorded for THBQ in biodiesel blend B20 at temperature 30℃ and at a concentration of 4x10-6 M which is the lowest concentration used compared to the concentrations of TBHQ used for the other metals (copper and stainless steel). Theoretical fitting of different isotherms, namely Langmuir, Freundlich, Kinetic-Thermodynamic and Flory-Huggins models were tested to clarify the nature of TBHQ adsorption on the three metal surfaces. The obtained experimental data best fitted Freundlich and Kinetic-Thermodynamic. In addition, the thermodynamic parameters of corrosion and adsorption processes were calculated and discussed. The sign of the Gibb’s free energy of the adsorption obtained suggested that inhibitor molecule has been spontaneously adsorbed onto the three metal surfaces. Positive values obtained for enthalpy change indicated that the adsorption of inhibitor is endothermic. The data clarified that the inhibition of aluminum and copper in biodiesel blend B20 by TBHQ takes place through physicochemical adsorption mechanism, while in stainless steel occurred by physical adsorption mechanism.
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