S-substituted derivatives of mercaptocarboxylic acid, one of the chelating agents, were examined as inhibitors of iron corrosion in a simulated cooling water. Polarization measurement of 99.99% Fe electrode rotating at 2, 000rpm was carried out in the cooling water with and without the inhibitor by a potentiostat and a dynamic IR compensator. The most effective inhibitor used in the experiment was 3-(S-n-octylmercapto) propionic acid, I, which inhibited the anodic reaction to a great extent without a change in the cathodic reaction of corrosion process. The inhibitor I was found to form a stable protective film on the surface in a thickness corresponding to trimolecular layer. The polarized reflection infrared spectra of the surface film agreed with those for the reaction product of I and Fe³⁺, identified with Fe(III)(n-C₈H₁₇SCH₂CH₂COO)₃. It was concluded that the inhibition by this inhibitor was attributed to the formation of stable and insoluble film consisting of the product, probably the chelate compound of I on the iron surface.

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Corrosion behavior of carbon steel, as affected by trace impurities in pure water (specific conductivity below 10μS/cm), was evaluated at room temperature. Impurities were added as sodium or magnesium compounds. Test water conditions were chosen to correspond to those of BWR primary coolant. The results indicated:
1) Corrosion was not promoted by addition of impurities in deaerated water containing oxygen below 5ppb. 2) Carbon steel was passivated in pure water (specific conductivity=0.06μS/cm) containing oxygen above 40ppb, however this state was unstable and corrosion was promoted by trace amounts of anions, prohibiting the passivity of steel. 3) The addition of anionic HPO₄^2- and OH^- did not promote corrosion, since the solution pH became more basic and carbon steel was easily passivated. However, some anions in neutral pH water containing oxygen adsorbed easily on the metal surface and prohibited the passivity of steel, thus lowering the corrosion potential and promoting corrosion. The ability to prohibit passivity decreased in the order SO₄^2->Cl^->NO₃^-. 4) Dissolved oxygen, at concentrations not high enough to inhibit corrosion promoted by anions, was found to accelerate corrosion.

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Two kinds of anodized passive films (EP and PP) on iron were prepared potentionstatically in a de-aerated 0.15N “neutral” boric acid-sodium borate buffer solution at room temperature. The anodic oxidation was conducted at +0.4V (SCE) for 1h for EP, and at +0.7V for 16h for PP. The final passivity maintaining current density was -60nA/cm² for the former and -3μA/cm² for the latter. These passive films showed two diffuse halos in their electron diffraction patterns and are likely to be amorphous. The short range order (SRO) structures of the passive films are derived through a radial distribution function (RDF) method applied to the haloed patterns. The SRO structures of the films were determined by using the gel structure model (GSM) which had been proposed for a ferric oxyhydroxide gel in our earlier work. In the GSM 16O^2- and 16OH^- ions occupy all of the 32e lattice sites in spinel structure while 16Fe³⁺ ions sit on some of the 8a tetrahedral (A) and the 16d octahedral (B) sites. The occupation fractions (AS and BS) on these sites may have different values depending upon the sample preparation conditions, where BS=1-AS/2. The estimated AS values of -0.78 for EP and -0.33 for PP correspond to value 0.8 of a slowly desiccated gel and 0.3 for a rapidly dried one, respectively. Namely, the well passivated film (EP) has essentially the same SRO structure as that for the gel slowly desiccated or well aged. The relationship between the SRO structures obtained in this work and the diffraction patterns reported for iron corrosion products by other investigators and ours is also discussed.

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The Nelson curves have been used for the selection of materials for equipment in high temperature and high pressure of hydrogen gas. These curves were determined empirically just in order to plot hydrogen attack behavior, so there is little transient analysis of such behavior. In order to study hydrogen attack behavior in long term testing, the anthers inserted test specimens made from seven commercial piping steels- (Carbon steel, C-1/2Mo, 1Cr-1/2Mo, 11/4Cr-1/2Mo, 5Cr-1/2Mo, SUS 304, SUS 316)- into a BTX chemical plant for 1 to 3 years. These test specimens were examined on the secular change of mechanical properties, microstructure and decarburization. In the present investigation, the results of the 1Cr-1/2Mo steel inserted in D-101 Line under the condition 516°C, P_H2=1.23MPa which were in the safety range of the Nelson curves, demonstrated distinct decarburization and decrease in mechanical properties. And on the austenitic stainless steels, which were reported immune to hydrogen attack, a slight decrease in carbon content was recognized at the temperature of 566°C and the hydrogen partial pressure of 4.4MPa.

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油田用水中におけるポンプ配管系統の腐食を検討するため, 45#鋼とステンレス鋼とをいろいろな面積比 (A₄₅#/A_SS) で接触させた状態で, 腐食電流, 腐食電位の検討を行った。
腐食電流は, A₄₅#/A_SS比が40以下であるときにはMansfeldの予測によく一致した。
ステンレス鋼との接触は, 原則的には45#鋼の腐食を促進するが, ガルバニ接触がステンレス鋼をカソードとして動作させる結果, ステンレス鋼の孔食発生防止に役立つことを明らかにした。

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