The effect of inhibitors such as sodium nitrite, dodecylamine and 1-hydroxyethylidene-1, 1-diphosphonic acid (HEDP) on erosion-corrosion of mild steel in 3% NaCl-SiC slurry was investigated by measuring the weight loss and the polarization curves. Tests were conducted with the test pot of a stirring cylinder type. When the inhibitor was added to the slurry, the effect of particle size on erosion-corrosion was greater than that of particle concentration. In the polarization curves of the slurry containing dodecylamine, the diffusion limiting current density of oxygen was increased by the addition of particles. The efficacy of each inhibitor was found to be greater in the order of HEDP 60ppm+Zn²⁺40ppm>dodecylamine (50ppm)>sodium nitrite (500ppm).

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When the exhaust gas of marine engine is passing the supercharger, the gas starts the compressor to supply the compressed air to the engine. The higher efficiency obtains the higher temperature of gas. The material of cast iron needed to cool by sea water because the material did not endure the exhaust gas temperature of 400°C. The temperature of sea water as cooling water is about 40-50°C. Sometimes, a lot of corrosion product was formed in water way of the supercharger and made a corrosion hole.
For comparison the corrosion products of supercharger with the ones of test pieces, the corrosion products on the test pieces produced with changing flow rate of cooling water or the temperature of test pieces under the similar environmental condition to supercharger. The test piece was made up of cast iron which was the same quality of the supercharger. The both corrosion products were analyzed by X-ray diffractometer to measure the intensity of diffraction of iron oxide and to identity iron oxide.
Six kinds of samples containing a corrosion product of damaged part in the supercharger were analyzed by X-ray diffractometer and X-ray fluorescent spectrometer. The results from X-ray diffractometer analysis, Magnetite and Fe(OH)₃ were observed in every sample, but Hematite or γ-Fe₂O₃ was missing somecase. The results from X-ray fluorescent analysis, calcium and silica were observed and calcium was rich in the damaged point.
For the similarity test for six samples in supercharger, the concentration ratio matrix method was applied to the data obtained from X-ray diffraction and X-ray fluorescent spectrometer. Finding the similarity among samples gave us very useful clues for consideration of origin of corrosion.
Using these data of test pieces, the origin of corrosion in supercharger estimated as follows: Magnetite of this damaged point was oxidized to Lepidocrocite by that the cooling water was running relatively slow and the temperature of wall of the water way elevated rapidly by running engine. This explanation is understood by iron oxidation process of Fe(OH)₂→Fe₃O₄→γ-FeOOH→γ-Fe₂O₃-α-Fe₂O₃.
The analysis of corrosion products by using with X-ray diffractometer and X-ray fluorescent spectrometer is very useful for the elucidation of origin of corrosion.

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Electropolished 99.99% aluminum sheets were heat-treated in air at 550°C for 15min to form a thin layer of thermal oxide containing γ-alumina crystals of sizes up to about 0.2μm. The thermally oxidized specimens were then anodized in 0.1M ammonium pentaborate solution at 20°C with a constant current density of 50A/m². Transmission electron microscopy and electron diffraction analysis of the stripped anodic films have shown that the films consist of amorphous, γ′ and γ-alumina. γ′-alumina occurs as band-like regions of relatively uniform widths surrounding γ-alumina crystals originally present in the thermal oxide. The width of the band of γ′-alumina was about 10 and 50nm for the films formed to 50 and 100V, respectively, indicating a relatively rapid development of γ′-alumina regions with increasing forming voltage. The development of the band of γ′-alumina was also found to be strongly inhibited when the thermally oxidized specimens were anodized in such solutions as aqueous ammonium dihydrogen phosphate, ammonium tartrate and ammonium citrate.

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The oxidation behavior of amorphous Fe-Si-B and Fe-Cr-Si-B, containing Cr of 10 to 19 at%, alloys was studied in a temperature range of 623 to 923K, under an atmosphere of 17 Torr O₂ and 3 Torr Ar for periods up to 6×10⁴s.
The SEM observation revealed that flowery agglomerates of oxide particles grew locally on the oxide film and they were distributed randomly.
The above was thought to be responsible for the observation that the oxidation kinetics did not follow any simple rate laws so far reported.
The oxidation rate has a minimum for the Cr content of 12 to 16 at% and this minimum corresponded to the highest peak of Cr profile in the oxide film shown by an IMA.
In the oxide film formed on the alloy without Cr, Si and B were enriched near the outer surface, while in that formed on the Cr-containing alloy Cr was enriched near the outer surface and the enrichment of Si and B followed next.

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In order to produce high corrosion resistance and ductility surface treatment layer, a Ni plating with the thickness of 10 to 40μm was performed on a high purity ferritic stainless steel with low C and N content. Then, the coated nickel layer was converted to Ni-Fe-Cr-Mo layer by a diffusion heat-treatment at temperature between 900 and 1100°C. For this treatment layer, the ductility, adhesion and resistance of the stress corrosion cracking (SCC) were investigated by SCC test in boiling 42% MgCl² solution. The results showed that this surface treatment layer had a good deformability and adhesion following plastic deformation of base metal, and improved the SCC resistance remarkably.

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