The anodic oxidation of aluminium was carried out in the electrolyte sulphuric acid to which was added glycerine. The product obtained was excellent in the thickness of film, hardness, and corrosion resistance.
The coating ratio increased with the concentration of glycerine until 5%, and gradually decreased above 5%.
The reason of the increase of the ratio should be assumed as follows: the temperature rise due to the heat generated during electrolysis may be prevented by the presence of glycerine, which would reduce the dissolution of coating into the electrolyte.

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The relaxation of internal stress of chrome plating was measured under various plating conditions to determine the degree of relaxation by heating and the following results were obtained.
1. Strong tensile stress was seen in thin layers, but it rapidly decreased with the increase of the thickness of layers and became almost constant in thick layers.
The thick plating layers deposited in low temperature bath had compressive stress. There was a close relation between the value of internal stress and the temperature of bath.
2. When chrome plating was heated at above 500°C, the tensile stress decreased and it was converted into compressive stress, which increased in linear proportion. The change of stress by heating had no relation with the thickness of plating.
3. The stress of pressed plating was relaxed by heating almost in linear proportion. It had no relation with the thickness, but the degree of relaxation at 600°C was above 90%.

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