Abstract
High molecular-weight mercaptan cannot be used as a corrosion inhibitor of Cu like amine in liquid media.
Ineffective adsorbability at lower temperature depends on defficiency of donating ability of an unshared electron-pair of S-atom of mercaptan. The defficiency can be made up by elevating temperature. Without the aid of being affected by the elevation of the temperature, suitable amounts of strong electron-donating substances, such as alcohol, ether, acid, ester, and amine, can enhance the adsorption of mercaptan. As those substances can, by hydrogen-bonding, draw H2O which is strongly adsorbed on Cu-surface even if dried, the spot where adsorbed H2O is forced to depart is refilled with mercaptan. S-atom in mercaptan donates its electrons to the metal by displacing H2O, schematically illustrated as follows:
M: metal, R: H or alkyl radical
Mercaptan acts as corrosion inhibitors when collaborated with electron-donating substances, such as alcohol, ether, acid, ester, and amine.
