The full name of hard anodic aluminum oxidation is hard anodic aluminum oxidation. The hard anodic aluminum oxidation treatment of aluminum alloy is mainly used for engineering or military purposes. It is not only suitable for deformed aluminum alloy, but also more likely for die casting alloy parts.

The thickness of hard anodic aluminum oxide film is generally required to be 25-150um. The thickness of most hard anodic aluminum oxide films is 50-80um, and the film thickness is less than 25um. The thickness of hard anodic aluminum oxide film is about 50um for parts used in tooth keys, spirals and other occasions. The thickness of anodic aluminum oxide film for wear resistance or insulation is about 50um. Under some special process conditions, It is required to produce hard anodic aluminum oxide film with a thickness of more than 125um, but it must be noted that the thicker the anodic aluminum oxide film is, the lower the microhardness of its outer layer can be, and the roughness of the film surface increases.

Sulfuric acid, sulfuric acid and organic sulfuric acid are added to the anode solution, such as sulfuric acid and sulfuric acid. In addition, the hard anodic aluminum oxidation treatment can be realized by reducing the anodic aluminum oxidation temperature or reducing the sulfuric acid concentration. For wrought aluminum alloys with copper content greater than 5% or silicon content greater than 8%, or die-casting aluminum alloys with high silicon, some special measures of anodic aluminum oxidation may also be considered. For example, for 2XXX series aluminum alloy, 385g / L sulfuric acid plus 15g / L oxalic acid can be used as electrolytic cell liquid in order to avoid burning of aluminum alloy during anodic aluminum oxidation, and the current density should also be increased to 2. Above 5A / DM.

Aluminum is a passive metal. Like titanium, tantalum, niobium and other metals, the surface passive aluminum oxide film is an important factor to provide protection. Therefore, anodic aluminum oxidation is a very effective means of metal protection.