THE REMOVAL OF OXIDE FILM FOR ALUMINIUM SURFACE

Abstract:Aluminum and aluminum alloys will naturally produce a layer of film on atmosphere which has the performances of eroding aesthetics,but the film is very thin and easy to rip,So it is necessary to remove the incomplete film at first before anodic oxidation,electronic plating or chemical plating for all kinds of aluminium work-pieces ,otherwise the next processes for anodic oxidation and electronic plating and the product qualities will be affected.

1.Aluminium Oxide Film

　　Various products of aluminum and aluminum alloys have excellent resistant performance on atmosphere because there is a thin and dense oxide film produced on the surface of this metal and its alloys.The film will thicken as the parking time on atmosphere increases,and the humidity is greater on atmosphere,the film is thicker.According to the differences of alloys and humidity,the thickness of films in a range of 5~200nm(50~2000A):the oxide film on the surface of aluminum and its alloys is not only produced on atmosphere,but also is oxidized by chemical methods or electrochemical anodic oxidation.The thickness of film obtained by chemical oxidation is about 1~3μm and the film produced by anodic oxidation is more than 100μm,which applies to decorations,sundry protective and abrasion-proof parts according to actual demand.Table 1 is that the thickness of oxide films produced by aluminum under a variety of different conditions.

2.The Removal Of Aluminium Oxide Film

　　Aluminum and aluminum alloys will naturally produce a layer of film on atmosphere which has the performances of eroding aesthetics,but the film is very thin and easy to rip,So it is necessary to remove the incomplete film at first before anodic oxidation,electronic plating or chemical plating for all kinds of aluminium work-pieces ,otherwise the next processes for anodic oxidation and electronic plating and the product qualities will be affected.

　　The removal of aluminium oxide film is mainly removed in alkaline chemical solutions,but also can be removed in acidic solutions,which is selected by the types of materials and the surface conditions of aluminium work-pieces.When there is a few of oil stains on the surface of aluminium work-pieces,it can remove oils and oxide films together.If the oil stains are heavy or the oil layer is thick,it should remove the oils first and then remove the oxide films,otherwise,it will cause the condition that the removal of oils and films incompletely to affect the next processes and reduce the qualities of surface treatment.The solution formulas and operating conditions of chemical solution immersion method to remove the oxide films of aluminium surface in Table 2.

3.The Removal Of Aluminum Anodized Film

　　After anodic oxidation of aluminium work-pieces or all kinds of sections,some work-pieces make the unqualified anodized films due to the misoperation of anodizing,cleaning,sealing,dyeing or other reasons,which needs to remove and anodize again for meet the requirement of product qualities.The removal of anodized films is different from the removal of natural films,the removal liquids are acidity and also can be alkalinity.The formulas and tech conditions of chemical removal liquids in Table 3.

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