Abstract
The corrosion inhibition of iron by propargylic alcohol (PA) in sulphuric acid was discussed by correlating the corrosion kinetics obtained by DC polarization measurements with surface structure obtained from AC impedance spectroscopy and IR spectroscopy. Both anodic and cathodic reactions were affected primarily by the addition of the inhibitor. Therefore PA can be appreciated as a mixed type inhibitor. The inhibition process was recognized as the substitution adsorption process. The number of water molecules replaced by one molecule of PA was 3. Standard free energy of adsorption, calculated at the corrosion potential Ecorr on the basis of Langmuir type isotherm, was –31.2 kJ mol-1.
Impedance spectroscopy revealed that the inhibitor adsorption was nonuniform and led to decreased surface heterogeneity and formation of the protective surface film. IR-spectra of PA-inhibited specimens suggested that the inhibiting film formed after prolonged immersion time at Ecorr was composed of mainly fully saturated hydrocarbons. The stable species of iron carboxylate and alcoxide contributed to strong adhesion of the film to the iron surface as well as to the protective properties of the film.
