THE ACTION OF POLAR ORGANIC INHIBITORS IN THE ACID DISSOLUTION OF METALS
TEXAS UNIV AT AUSTIN CORROSION RESEARCH LAB
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A mechanism based on recent advances in the field of chemisorption on metals is presented for inhibition by polar organic compounds. Electrostatic bonding at the cathode areas contributes to the over-all inhibition. However, polarization of anodic dissolution because of chemisorption of the inhibitor is more pronounced than cathodic polarization. Inhibitor chemisorption occurs through coordinate covalent bond formation with surface atoms of the metal. This mechanism satisfactorily explains the dependence of inhibitive power on the electronic structure of the functional group, on the solubility, and on the substituents of the inhibitor. The theory allows for different metals and permits positive and negative temperature coefficients. Sterochemical effects occur, but they are of less importance than previously thought. The results reported in the literature for N- and S- containing compounds, aldehydes,and ketones are in agreement with the mechanism. The effect of the ethylenic linkage in the inhibitor and the ortho effect are also consistent with this mechanism.
- Organic Chemistry