In the previous papers, the authors proposed that organic corrosion inhibitors could be adsorbed on metal surface by displacing adsorbed water. For example, amine acts as an inhibitor for metals in corrosive media in the following manners.
When the inhibitor is insufficiently added to the media, an active site, which is given by M at the stage (II), may be exposed to corrosives and subsequently the metallic corrosion may proceed. In this report, the corrosion and the corrosion inhibition processes of Fe and Al in the state corresponding to the stage (II) were examined in aqueous and non-aqueous corrosive media with the amine inhibitor. The reaction of Fe or Al with alkyl bromide in the non-aqueous media took place by the addition of N, N-dimethyloctylamine at about 10^-5mole/g-metal. Al was corroded to more extent in 0.05N aqueous alkaline solution with 10^-5mole/g-Al of the amine than in the uninhibited solution. In each case the metallic corrosion was most promoted with the approximately equal amount of the amine and the reaction was completely inhibited by the addition of amine at 10^-3mole/g-metal. Moreover, water could inhibit the reaction in the non-aqueous media. In the aqueous media as well as in the non-aqueous media, water might be an inhibitor for the metal. But, because of being strongly associated with bulk molecules in general, water may not be adsorbed on the metal in the aqueous media, even if the electron-accepting sites may be brought about by the desorption of the adsorbed water.

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By comparing with dicyclohexylammonium nitrite which has been known as one of the most excellent vapor phase rust-inhibitors, the inhibiting effect of various compounds including hexamethylenetetramine (HMT) was investigated, and the findings are summarized as follows: 1) HMT is proved to be remarkably excellent as a vapor phase rust inhibitor. Particularly, as HMT is well water-soluble, it is possible to make an excellent vapor phase rust-inhibiting paper from it by using a water-soluble binder. 2) The liquid amine compounds are able to maintain the inhibiting effect for a relatively long time at the normal temperature, when these were absorbed on an absorbent. 3) At the normal temperature, the liquid carboxylic acids and dibasic acids show none of inhibiting effect but some accelerating effect of corrosion. The solid fatty acids with small numbers of carbon are good in the inhibiting effect. The ortho compound of aromatic acids shows also a good inhibiting effect. 4) As a quantitative measure of inhibiting effect, the ratio of the rusting area to the total surface of the iron test piece was measured by using a microscope (150 magnification) with an area-measuring lattice net. The relationship between the inhibiting effect and the amount of the binder was also determined. 5) On the basis of the results of ATR (Attenuated Total Reflection) spectra and X-ray diffraction on the surface of the iron test piece treated by the vapor phase rust-inhibitors, the adsorption or the formation of complex salts could not be found. When the iron piece was treated by succinic acid, a remarkable rust was generated and it was confirmed by X-ray diffraction that the rust consists of α-Fe₂O₃·H₂O.

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Resistance of cold rolled steel sheets after annealing to the initial atmospheric corrosion, pin point rusting, could be estimated by using autoreduction phenomena of air-formed films in a neutral solution. This fact has suggested that the rust formation should be initiated by the dissolution of iron at the defects in the oxide film and the rusting resistance is controlled by the stability of the oxide film. It was found that this stability of the oxide film was affected remarkably by steel components, e. g. Mn, S, Sb, and Cu. From the fact that both Mn and S decrease the autoreduction time τ of the oxide film by restraining the growth of γ-Fe₂O₃ and S exists substantially as manganese sulfide in the annealed steel, manganese sulfide seems to be responsible for the formation of defects in the oxide film, and also accelerates the iron dissolution as an anodic stimulator. On the other hand, Sb which increased τ values and made γ-Fe₂O₃ film tight in coexistence with Cu, functioned to cancel the undesirable effects of the sulfide so that the rusting resistance of Sb-Cu steel was superior to that of plain steel. Furthermore, Mn in solid solution, which resulted in formation of an unknown amorphous oxide on steel surface during tight annealing, improved the rusting resistance in wet corrosion.

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Four kinds of tar-epoxy paints and two kinds of zinc rich paints were applied to the I-shaped steel piles of 12m in length, and these six painted steel-piles were driven into the sea along with an I-shaped bare steel-pile. After about six years, the seven test steel-piles were pulled out and the performance of the paints in marine environments was examined. The obtained results are summerized as follows: (1) It has been observed that the performance of the paints at harbours depends on the kind of paint and marine environments. Especially, since the performance of tar-epoxy paints largely depends on the kind of paint, the paint for given conditions should be properly selected in applying to steel structures. On the other hand, the damages of zinc rich paint films were found just below the high water level in case of paint No. 6 and near the low water level in case of paint No. 5. (2) Corrosion is likely to localize at projecting portions directly under the mean low water level, but in the cases of paint No. 1 and 6 the localized corrosion was rarely found. (3) The damage of paints and the subsequent rust initiation due to the friction in driving piles were observed for all of the tested piles in the range of 2 to 3m from the bottom end.

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