Research And Application Of Alkaline Chemical Polishing On Aluminum Alloys Surface

Polishing technology can be utilized to improve the surface finish,flatness and decorative effect of aluminum-alloy products,which has played an important role in increasing the added values.The background of common polishing technologies was introduced in the thesis.Alkaline chemical polishing,as a kind of polishing technology,has several characteristics such as low-cost,no pollution,simple operating,and polishing liquid post-processing,which is accorded with environmental protection and further needs exploring.Based on previous results of the alkaline chemical polishing from literatures,the detail experimental projects were designed and carried on,including polishing time and temperature,optimization of polishing liquid composition contents,passivation post-processing.The main contents of the present research are given as follows:(1)Aluminum-alloy plates such as 6061# and 5052 # were used as the substrate plates to investigate the influence of temperature and time on the polishing effect.The testing results showed that the aluminum-alloy plates could get higher gloss at the polishing temperature of 50~65 oC for 10~30 s.With the increase of temperature and time,the weightlessness of aluminum-alloy plates increased gradually.(2)The influences of various components on the polishing effects of the 6061# aluminum-alloy plate were investigated by many tests.The influences of sodium hydroxide,sodium nitrate,sodium silicate and potassium fluoride were explored and the optimized concentrations include sodium hydroxide of 250 g/L,sodium nitrate of 150 g/L,sodium silicate of 15 g/L,and potassium fluoride of 13 g/L were defined under experimental conditions.And function of additives including ammonium molybdate,thiourea,ethylenediamine tetraacetic acid,and hexamethylenetetramine as corrosion inhibitor,zinc sulfate,nickel chloride and copper sulfate as metal salt,sodium dodecyl benzene sulfonate and sodium citrate as surfactant was also studied in detail.The experimental results showed that corrosion inhibitors may obviously improve the polishing effect.The comprehensive effect is relatively good,when the concentration of ammonium molybdate is 40 g/L in polishing solution.Inorganic metal salts could improve the gloss of aluminum alloys,but increase weightlessness.Both sodium dodecyl benzene sulfonate and sodium citrate could improve the gloss of aluminum products,reduce weight loss,but the effect was slightly worse than that of corrosion inhibitor.And the polishing effect of 5052# aluminum-alloy plate is much worse than that of 6061#.The effect of ammonium molybdate was significantly analyzed by orthogonal experiments,which may enhance the influence of additives on polishing effect.Moreover,it was found that the aluminum-alloy plate area of ca.45 dm2 can get high gloss when polished by one liter of selected polishing liquid solution through continuous polishing testing.(3)Normally,passivation treatment for aluminum-alloy plate need polishing in the alkaline polishing solution,it was found that the passivation effect of rare earth passivation is obviously better than that of zirconium titanium passivation.The obtained passivation film is more obvious.Optimal formula and technological conditions for rare earth passivation solution include cerium nitrate of 15.0 g/L,potassium permanganate of 4.0 g/L,sodium nitrate of 1.2 g/L,passivation time of 15~25 min,and passivation temperature of 30~40 ?.