Study On Technique And Its Decoration Of The Anodic Oxide Film For Al-Si-Zn-Mn-Mg Series Die-cast Aluminum Alloy

Aluminum alloy die-casting technology is a high-efficiency,non-cutting metal forming process,which is widely used in the manufacturing of industrial products.Its advantages are that it can be manufactured by other processes that are difficult to be formed,complex shapes of workpieces,high utilization of materials,and high production efficiency,but the surface treatment of die-cast aluminum alloy has greater difficulties.Therefore,aluminum alloy die-casting usually shows low wear resistance and corrosion resistance,poor color appearance,and single decoration.Anodizing technology is the most popular surface treatment technology for aluminum alloys in modern times.Its advantages are that the electrolyte used in anodizing is low in cost,simple in process,easy to operate,and has a wide range of applications,which is in line with the current concept of green circular economy.In addition after the anodizing process,the generated oxide film and the alloy substrate have a very good bonding force,abrasion and corrosion resistance of the film layer,strong metal texture,full color,and excellent decorative effects,which are suitable for the goals of die-casting aluminum alloy surface treatment.In order to expand the surface decorative properties of die-cast aluminum alloys,this article explores the anodization of die-cast aluminum alloys and obtains the following results:(1)An Al-Si-Zn-Mn-Mg series die-cast aluminum alloy suitable for anodizing and coloring was determined.The composition was optimized and the alloy composition was Al-0.8%Si-4%Zn-2%Mn-0.5%Mg.(2)The sulfuric acid solution was used as the basic electrolyte for the anodizing of Al-Si-Zn-Mn-Mg series die-cast aluminum alloys.The optimum process parameters for the sulfuric acid anodizing method were determined:the sulfuric acid concentration was 20%;Current density is 1.5 A/dm2;oxidation temperature is 20℃;oxidation time is 60 min.(3)Adding oxalic acid,tartaric acid,citric acid and sulfuric acid to form a mixed acid system during the anodizing process,discussing the effect of organic acid addition on the performance of the film under different mixed acid systems,and finally determining the best suitable for anodizing of die-cast aluminum alloy Mixed acid system concentration:10%sulfuric acid plus 15%citric acid mixed acid system.(4)The electrolytic coloring process was researched after the anodizing of die-cast aluminum alloy.Through comparison of five electrolytic coloring solutions,it was determined that the electrolytic coloring solution suitable for Al-Si-Zn-Mn-Mg die-casting aluminum alloy was selenium salt.Solution.The process parameters are:electrolysis voltage 18 V;electrolysis temperature 25℃;solution pH 2;electrolysis time 15 min.