Corrosion inhibition of picolinic acid and ascorbic acid mixture by 5-hexyn-1-ol

Abstract

Inhibition of carbon steel corrosion in a deaerated solution containing a mixture of picolinic acid (3.5×10^-2 M) and ascorbic acid (1.0×10^-2M), effective for magnetite film removal, by 5-hexyn-1-ol has been studied between 30 to 70°C by weight loss and electrochemical impedance techniques. The effect of inhibitor concentration and the reaction temperature on

the performance of inhibitor has been evaluated. Activation energy for carbon steel corrosion decreased upon the addition of 5-hexyn-1-ol suggesting that the mode of operation is by chemisorption of the inhibitor on the metal surface. The inhibitor efficiency increased with temperature confirming to the chemical nature of adsorption process. The thermodynamic parameters such as free energy, heat and entropy of adsorption of the inhibitor on carbon steel surface have been determined. 5-hexyn-1-ol has been shown to follow Bockris-Swinkels isotherm leading to the replacement of four water molecules per inhibitor molecule adsorbed. Impedance measurements showed that the addition of inhibitor affects the charge transfer process on exposure for longer duration. While the charge transfer resistance increased in presence of 5-hexyn-1-ol, the double layer capacity showed reverse trend.