In order to find out the factors affecting dispersion of data in Corrodkote test, some experiments were carried out by means of an experimental designing method. The levels to make the dispersion small were as follows: 1) The Corrodkote paste is thickly applied to test specimens, which are then allowed to dry at the ambient temperature for 1hr before being placed in a humidity chamber. 2) Relative humidity of the exposure zone of the chamber for test cycle is maintained between 87 and 94 percent. 3) After the test cycle, the specimens are cleaned in running water using a piece of clean absorbent cotton with mild abrasive such as water paste of cleanser. 4) The points of corrosion failure are redeveloped for 2hr between 80 and 88 percent relative humidity. 5) The extent of corrosion of the specimens or other failures were examined in a lattice of 2.5×2.5mm dimensions.

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Surface hardening treatments, such as TiC-coating by CVD process, have recently been used to prolong the lives of cemented carbides for cutting tools, working dies, etc. This paper concerns with the surface chromium carbide layer on cemented carbides as formed in fused borax bath containing pure chromium metal powder, and also the oxidation and corrosion resistances of the cemented carbides thus treated. The layer of Cr₇C₃ was easily formed on cemented carbide, when samples were immersed in the bath containing pure chromium metal powder. Parabolic law can be applied to the relation between the thickness of the Cr₇C₃ layer and the treating time. The layer was thought to be formed by the reaction between atomic Cr and WC dispersed in the cemented carbide, or C dissolved in Co binder. Oxidation resistance of the cemented carbides below 900°C was remarkably improved by the chromium carbide coating. Corrosion resistance against 10% HNO₃ or 10% H₂SO₄ aqueous solution was also improved.

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Anodizing of 99.99% aluminum foil in 250g/l maleic acid containing 0.8-4.4g/l H₂SO₄ was carried out for 30 minutes at 30°C and a constant current density of 2A/dm². The oxide film was then isolated from the substrate by dissolving aluminum in Br₂ -CH₃OH. After having been heat-treated at 400-900°C for 20 minutes, the film was investigated by means of visible and infrared spectra, ESR spectrum, X-ray diffraction, and quantitative chemical analysis of SO₄^2-. The maleic-sulfuric acids film was decolored when heated at more than 500°C, and the films formed in the baths of higher concentrations of H₂SO₄ were more easily decolored. Heat decomposition of organic compounds and SO₄^2-ions in the film and structual change of the oxide film did not correlate to the change in decoloring temperature of the film. However, the change in relative intensity of ESR adsorption, which was supposed to be caused by carbon radical of -COO (-) in the film, corresponded quite well to the decoloring process. The decoloring of the film was thought, therefore, to be caused by the state change of -COO (-) with a decrease in the amount of carbon radical before the organic compounds were finally decomposed to CO₂ gas.

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A wear testing was made in accordance with Falex method by using Cr-Mo steel test bars quenched and tempered after chromizing treatment; V-blocks of the testing machine were also quenched and tempered through gas carburizing. Besides, comparative tests were made with the test bars treated through gas carburizing. It was revealed, from the test, that quenching and tempering after chromizing give more excellent wear resistance than the quenching and tempering through gas carburizing. However, there was little effect of chromizing with test samples having thin Cr-layer. Furthermore, it was found that the tempering temperature considerably affected the wear resistance in the case of chromizing. It was concluded that the tempering temperature range for good wear resistance was from 200 to 300°C.

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