The softness of decamethyleneimine （CH₂）₁₀ NH as a base was evaluated using the relationship between the inhibition efficiency, I and the softness as a base, E_n. The value thus obtained was E_n＝2.43, remarkably high, depending on π-characterized unshared pair of electrons at the N atom caused by strain in the ring.

Coated steel structures are periodically re-coated due to deterioration of the coated film. To obtain a good resistance to corrosion after re-coating requires a fully sufficient removal of rust and residual film from the steel plate surface, through preparation of that surface. Clarification of the post-coating corrosion resistance of steel plate with an adherence of metal constituents deriving from the plated film and wire material will presumably provide knowledge useful for establishing the optimal method for surface preparation. This study consequently examined the effect exerted on post-coating corrosion resistance by metal constituents adhering to the steel plate surface. It found that coated steel plate whose surface had been prepared with a zinc-plated wire brush yielded a good resistance to corrosion as compared to other coated steel plate. To determine the cause, an examination was made from the perspectives of electrochemical properties, composition analysis, and surface free energy. The results indicated the possibility that corrosion products in the slight traces of zinc adhering to the steel plate may have curtailed the progress of corrosion by acting as a barrier to the diffusion of oxygen.

A new method to evaluate the corrosivity of tap water to carbon steel has been proposed. Corrosion tests for the tap waters sampled at 49 locations throughout Japan were conducted. Average corrosion rate v_w and maximum one v_max were measured. Relatively close relationship of v_w and v_max to concentration of SiO₂ and SO₄^2－ were found. On the other hand, the corrosion rates showed slight dependence on concentrations of Cl^－ and HCO₃^－. These facts are contradictory to the conventional knowledge. Furthermore, the authors surmised that [SO₄^2－]/[SiO₂], named SS ratio, was an effective Corrosion Index. SS ratio showed closer relationship to v_w and v_max than Langelier Index, Ryznar Stability Index and Larson-Skold Index. The authors succeeded in expressing v_w and v_max as a function of only SS ratio.