アミン類を主剤とする防食剤の研究 (第47報)

第1アミンと第3アミンの挙動的差異

抄録

In our previous reports, we concluded that active sites on metal, where two types of organic corrosion inhibitors could be adsorbed, were anchored with two types of water, one by its electron donation and the other by its proton donation. When the water was desorbed, electron-accepting sites and proton-accepting ones would be revealed on metal. Electron-donating species, such as RN (CH₃)₂ (or ROR'), could be adsorbed by displacing the water only on the electron-accepting sites, while those species which could act as proton donors and as electron donors, such as RNH₂ (or ROH), could be adsorbed on both sites.
In the present work, investigation on the electron-accepting sites was mainly carried out in non-aqueous media. Hydrogenation of olefines with Ni-catalysts was most promoted by the addition of the limited amounts of tertiary amine (10^-5M/g-metal) and by further addition it was retarded because of poisoning Ni. Ni powder was acceleratedly corroded by alkylhalides with the amounts of the amine and further addition over the amounts inhibited the corrosion. These acceleration should take place, as the water anchored by its electron donation was forced to depart from metal surface by the amine exposing electron-accepting sites. When the electron-accepting sites were again adsorbed with electron-donating species such as tertiary amine, corrosion inhibition would be made up. When the sites were exposed to reactants such as olefines or alkylhalides because of insufficient amounts of the amine, the catalytic hydrogenation or the corrosion would easily take place.
With primary amine, reproducible results as presented with tertiary amine could not be obtained. For these phenomena, it is supposed that primary amine can be adsorbed by two ways differing from the case with tertiary amine and conflicting data will be brought about.