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

Inhibition of carbon steel corrosion in a deaerated solution containing a m ixture of picolinic acid (3.5 x 10(-2) M) and ascorbic acid (1.0 x 10(-2) M ), effective for magnetite film removal, by 5-hexyn-1-ol has been studied b etween 30 to 70 degreesC by weight loss and electrochemical impedance techn iques. The effect of inhibitor concentration and the reaction temperature o n the performance of inhibitor has been evaluated. Activation energy for ca rbon 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 met al 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 car bon steel surface have been determined. 5-hexyn-1-ol has been shown to foll ow Bockris-Swinkels isotherm leading to the replacement of four water molec ules per inhibitor molecule adsorbed. Impedance measurements showed that th e addition of inhibitor affects the charge transfer process on exposure for longer duration. While the charge transfer resistance increased in presenc e of 5-hexyn-1-ol, the double layer capacity showed reverse trend.