High speed anodizing of aluminium to form functional composite oxide films

建立了在铝表面形成复合阳极氧化膜的两步工艺，即步骤I(通过电解或浸渍方法在铝表面形成金属氧氢氧化物薄膜，然后根据需要进行干燥或热处理)*步骤II(通过在酸性溶液中的阳极氧化在铝表面形成多孔氧化膜)。对于第二步，采用含Mn(II)盐的硫酸溶液实现了高电流密度的高速阳极氧化，得到的氧化膜的硬度始终高于相同条件下形成的常规氧化膜。此外，根据步骤I所用的方法，方法(A)获得具有极高硬度和高耐磨性的黑色阳极氧化膜，(B)和(C)使膜具有显著的抗点蚀性能。尝试提高膜介电常数的方法(D)是不成功的，但在实验中发现，在含有Ba(II)盐的溶液中沸腾可以有效地修饰阳极氧化膜，并在步骤II中将其应用于硫酸工艺，生成含结晶BaSO4的复合氧化物。添加Mn(II)盐的硫酸溶液使Al能够高速阳极氧化，对于难以在其上形成均匀阳极氧化膜的铝合金也是有效的。

A two-step process to form composite anodic oxide films on Al, that is, step I (formation of metal-oxyhydroxide film on Al by electrolysis or dip methods, then drying or heat treatment, if necessary) * Step II (formation of porous oxide film on Al by anodic oxidation in acid solutions), was established.For Step I,(a) electrolytic treatment in molybdate solutions, (b) chromate treatment, (c) chromate-phosphate treatment, (d) electrolytic treatment in Ti (IV) containing solutions, and related methods were carried out. For Step II,the high speed anodizing with high current densities was realized by using sulfuric acid solutions containing Mn (II) salts.The anodic oxide films obtained by the above process always showed higher hardness than the conventional films formed under similar conditions. Further, depending on the method used for Step I,method (a) gave black anodic oxide films having very high hardness and high wear-resistance, (b) and (c) gave the films markedly resistant to pitting corrosion. Method (d), which was attempted to increase dielectric constant of the film, was unsuccessful, but during the experiment it was found that boiling in solutions containing Ba (II) salt is effective to modify anodic oxide films and forms composite oxide containing crystalline BaSO_4 when it is applied to the process using sulfuric acid for Step II.The Mn (II) salt added sulfuric acid bath enabled to anodize Al at high speed, and was found also to be useful to anodize Al alloys on which formation of uniform anodic oxide film is difficult.