Influences of environmental corrosive liquids on cavitation erosion of commercially pure iron were investigated using the magnetostriction vibratory facility. As a result, it was made clear that the environments exert two kinds of influence on erosion which are opposite to each other: one is to accelerate erosion by extending and widening the cracks over the damaged surface, another is to inhibit erosion through adsorption of Cl^- ion on the surface. Thus erosion is sometimes accelerated by environments (in the case of corrosive liquids of pH 2 and pH 12) and sometimes is inhibited (pH 4) depending on the relative intensities of the influences. Furthermore, the intensities vary according to the damage processes of erosion. Combining the results with that of the previous paper, an equation has been proposed to estimate the amount of damage of the material under the simultaneous attack of erosion and corrosion.

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The effect of γ-ray irradiation on the corrosion of SS 41 carbon steel in high temperature water was studied. The average corrosion rate was measured after 48 or 96hr exposure to distilled water containing different DO (5-700ppb) at 250°C. The amount of Fe ions in the film and that dissolved in water were separately determined by weight measurement combined with a film dissolution technique. The composition of oxide films was determined by X-ray photo-electron spectroscopy (XPS) and X-ray diffraction. After 48hr the corrosion rate with γ-ray irradiation was larger than that without irradiation, whereas after 96hr no detectable difference was observed. By X-ray diffraction the bulk composition of the oxide film was found to be mainly magnetite. XPS showed that γ-ray irradiation forms unknown oxygen compounds, OX, other than O^2- and OH^-, and also graphite-like substance on the surface. The intensity of the carbon spectra was three to four times higher when γ-rays were irradiated. It is considered that the mechanism of corrosion under γ-ray irradiation is different from that without γ-ray. The corrosion rate and the surface composition showed no clear relationship with DO in the range examined in this work. It is interesting to note, however, that the average dissolution rate of Fe increases with the amount of OH^- (without γ-rays) or OX (with γ-rays) on the oxide surface.

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Stress corrosion carcking (SCC) susceptibility of various austenitic stainless steel pipe welds has been studied by means of constant load tensile tests and pipe tests in 288°C water containing 26ppm dissolved oxygen. The results obtained are summarized as follows: (1) SCC susceptibility of SUS 304 pipe welds is comparatively low under the condition of as-welded. It becomes, however, high remarkably by grinder operation and/or low temperature sensitization heat treatment. The distribution of time to failure on SUS 304 pipe welds can be expressed as a log-normal or Weibull distribution. (2) SUS 304L, 304NG, 316NG, and 347 stainless steel pipe welds have a good SCC resistance and sensitization resistance. Furthermore, the life estimation on alternate pipe welds was conducted statistically.

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Factors that control paint adhesion loss of cathodically deposited sheets in the water immersion test have been investigated using various metal substrates such as steel sheet, galvanized sheet, electroplated sheet and phosphated sheet.
By applying Sand's equation to the cathodic electrodeposition, it is found that the pH at the electrode surface increases to about 12. In such a highly alkaline condition, a dissolution of both metal substrate and phosphate film occurs during electrodeposition, and results in reduction of the bonding strength between the phosphate and the substrate. Therefore, the paint adhesion in the water immersion test depends on the dissolution of the surface layers (phosphate and substrate).
This fact suggests that the paint adhesion loss can be estimated by the solubility of the surface film in an appropriate alkaline solution (for example, pH 12-13 of NaOH solutions).
The solubility of the plated sheets in the alkaline solution greatly depends on the coated materials and the solubility of the phosphate film decreases with increasing phosphophillite content.
Further, a new parameter which is determined by the critical time of the electrodeposition has been proposed for the estimation of the corrosion resistance of the painted sheets.

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In order to qualify stainless steel as structural material for transport containers to carry crude phosporic acid, corrosion tests were conducted on various types of stainless steel.
The results obtained from the tests indicated that the alloying metals most effective in increasing corrosion resistance against crude phosphoric acid are Mo, Cr and Cu. Of these three, Mo and Cr enhancing the passivation of stainless steel are particulary effective.
Based on this finding, stainless steels of high Mo and/or Cr content-317L and 25Cr-4Ni-2Mo steel-were tested to determine the influence of impurities contained in crude phosphoric acid on the corrosion behavior. The impurities found to accelerate corrosion were H₂SO₄ and F^-; impurities, on the other hand, that inhibited corrosion were Fe³⁺, Mg²⁺, Ca²⁺, Al³⁺. The action exerted by these impurities on the corrosion can be explained electrochemically, based on the results of measurements of anodic polarization curve in a solution containing these impurities singly or in combination: In solutions containing both H₂SO₄ and F^-, the critical current density for passivation and the passive current density were found to be markedly raised, whereas the solution containing Fe³⁺ was found to have the corrosion potential of stainless steel shifted from the active to the passive region.
Better corrosion resistance was found to be provided by the 25Cr-4Ni-2Mo than by the 317L steel.

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This report described the high temperature coatings for protecting hot components in gas turbines. The Coatings covered the range from simple chromium and alumium metals formed by pack cementation to the more advanced physical vapor deposition, developmental low pressure plasma flame spray and the combined treatments.

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