292-299Inhibition 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