アミン類を主剤とする防食剤の研究 (第28報)

インヒビターの会合性と吸着能力-その2

抄録

An influence of self-association of high molecular-weight amine-type corrosion inhibitors upon their chemisorption on a metal has been studied. In the earlier report, it has been also pointed out that ability of the adsorption decreased when intermolecular association of the inhibitor occurred with an other proton donor or acceptor. Two types of intermolecular association can be assumed to occur, (1) between the inhibitor and a proton donor and (2) between the inhibitor and a proton acceptor.
Extents of these associations were determined with infrared adsorption spectra, and simultaneously, inhibition efficiencies were obtained in the corrosion tests conducted in 5% hydrochloric acid with filmed mild steel test coupons dipped into carbon tetrachloride solution of the inhibitor associated or not. The inhibitors employed are 2-n-dodecyl pyrrole (I), N-n-dodecyl pyrrole (II), and dimethyl cetyl amine (III).
When II or III was associated with other proton donor such as methyl alcohol, pyrrole, phenol, or acetic acid in carbon tetrachloride, the inhibition efficiency was found to decrease. This result indicates that the association causes the chemisorption ability of inhibitor to lessen since active hydrogen of the proton donor blocks an unshared pair of electron of the inhibitor with hydrogen bond. Increasing efficiencies of these inhibitors in high concentration of acetic acid solution, however, may suggest a possibility of the chemisorption of inhi bitor associated with it.
The low inhibitions were observed in the tests conducted with the coupons filmed in the solution containing I and such a proton acceptor as dioxane or triethylamine. Though an association between the inhibitor and the proton acceptor was determined to take place, it seems unreasonable to assume that the decrease of inhibition depends upon the association, because of no blockade at the unshared electrons of the inhibitor.