Anodizing of aluminum is widely applied for many aluminum products to improve the corrosion and wear resistances. It is well known that cracks in anodic oxide films occur at relatively sharp corners of aluminum parts. These cracks at the corners promote the corrosion of aluminum products. In order to prevent the formation of the cracks, it is generally recommended that the sharp corners of aluminum parts should be changed to round corners. In this paper, the formation of the cracks in the anodic oxide films at the corners of aluminum parts was theoretically analyzed using FR value defined in this paper as the film formation ratio ; and then two theoretical equations were derived. One equation gives the angles of the cracks at the sharp corners of aluminum parts, and the other equation gives the critical radius of the occurrence of the cracking in anodic oxide films at the round corners of aluminum parts. Experimental results revealed that the theoretical angles of the cracks in the anodic oxide films at the sharp corners agreed with the experimental ones, and that the critical radius of the crack formation at the round corners calculated by the theoretical equation agreed with the experimental ones using the value of elongation ratio, P=0.003.
The effect of oil dissolution by electrolyzed acidic solution was confirmed. As a result of that, the electrolyzed acidic solution obtained by electrolysis with a dilute sodium chloride and sodium sulfate solution was found to dissolve oil remarkably well, but while an ordinary acidic solution which was arranged to have the same pH as the electrolyzed acidic water hardly dissolved oil at all. The oil dissolution was assumed to be caused by the high concentration of dissolved oxygen contained in the electrolyzed acidic water. The electrolyzed acidic water of the sodium chloride solution thus decomposes a part of the oil. It was aiso recognized to have other effects, such as hydrophilicity and to produces several kinds of volatile byproducts. Since the electrolyzed acidic water of sodium sulfate did not show this kind of phenomenon, the oil decomposition was suspected to be caused by hypochlorous acid occurring at anode electrode during the electrolysis of the sodium chloride solution.
A titanium redox process was proposed as a novel nickel electroless plating method with zeroemission. In this process, the Ti(IV) formed during electroless nickel plating was electrolytically reduced to Ti(III), which was simultaneously recycled using a regeneration system as a reductant for the plating solution. As an industrial example of applying this technique, trial manufacturing of the nickel metal foam (Celmet®) was considered as a current collector for Ni-MH batteries was considered. Celmet® was currently being produced by the following procedure : conductive treatment of urethanfoam, nickel electroplating, and burning away urethane under a reducing atmosphere. Applying this novel technique for this conductive treatment, it was proved that the conductive treatment of urethane continuing beyond 100 hours was possible in the pilot plant scale operation. Furthermore, as a result of a charge-discharge test of the obtained Celmet® anode used in a Ni-MH battery, the cycle life of the Ni-MH battery obtained from this process was far longer than that in a battery obtained from the Ni electroless plating method using sodium hypophosphite.