Abstract
Tertiary amine can be adsorbed on metal only by electron donation, while primary amine can both by electron donation and by protonation. Proton-accepting sites are left unadsorbed on the metal surface treated with electron donating species. On the sites hydrogen sulfide can anchor because of its protonation ability like protonating inhibitors, such as, benzotriazole and 2-mercaptobenzothiazole in acid solution. When tertiary amine is adopted as inhibitor for the metal in a corrosive solution, protonating species can be further adsorbed. After the solution was inhibited with N, N-dimethyldodecylamine, 2-mercaptobenzothiazole could anchor on the metal by hydrogenbridging, as it had an active hydrogen atom belonging to its S-atom. In NaCl solution which was acidified with acetic acid undissociated hydrogen sulfide could also be adsorbed on the metal in the same manner as 2-mercaptobenzothiazole, after finishing the preliminary treatment with N, N-dimethyldodecylamine. Hydrogen penetration into mild steel sometimes originates in the adsorption of hydrogen sulfide.
