Pre-treatment of aluminium alloy anodising

Pre-treatment of aluminium alloy anodising

　　Aluminium is extremely unstable in the air and easily generates oxide films that are difficult to identify with the naked eye. Due to the different casting processes of aluminium parts, or direct shearing from extension plates, or mechanical fine processing, or after different processes and heat treatment or welding, etc., by the above-mentioned different processing processes, the surface of the workpiece will leave different states, different degrees of dirt or traces, in the pre-treatment process must be based on the actual situation of the surface of the workpiece to choose the pre-treatment process method.

　　Fine processing parts in the pre-treatment process need to pay attention to the problem: fine processing parts although the surface of the natural oxide film before the first generation, easier to remove, but delicate heavy, especially in and around the eyelet (due to the need for lubrication in the machining process and added), such workpiece must first be cleaned by organic solvents, if the direct use of alkali wash not only greasy heavy difficult to remove, and fine processing surface can not withstand a long time of strong alkali corrosion, the results It will also affect the roughness of the surface of the workpiece and the tolerance of the fit, and eventually become scrap.

　　Casting molding parts in the pre-treatment process need to pay attention to the problem: casting molding parts are not all surfaces are mechanically processed, the surface without machining to leave the casting process formed during the thick oxide layer, some also sand layer, in general, machining or sandblasting methods to remove the original oxide film in this part, or by alkali washing and then processing, only in this way can not only remove the original oxide layer of the unprocessed parts Only in this way can the original oxide layer of the unmachined part be removed, and the change of tolerance size of the machined part be avoided.