Research On Chemical Polishing Of Aluminum And Its Alloys Favourable Of Environment Protection

Chemical Polishing is a kind of very important process on surface treatment of aluminum and its alloys. Chemical Polishing can make the surface smooth and bright,increase light and thermo reflection ability,enhance corrosion resistance,etc. Traditional Chemical Polishing is etching aluminum products in intermixture of phosphoric acid,sulfuric acid and nitric acid. But in this process there was oxynitride gas give off,like yellow fume. It caused serious air pollution,damage to human's health. So,purge the "yellow fume" is necessary.Now there are some Chemical Polishing methods without yellow fume,but use these polishing methods we couldn't get the surface as bright as used traditional Chemical polishing,sometimes may cause pitting corrosion. So these methods still can't instead of traditional Chemical Polishing,only some situation not required the surface too bright may use these methods.After inquired lots of documentation and analysisd,we decide to exploit a new technique of Chemical Polishing which can increase surface lightness and avoid pitting corrosion. The new technique based on miscible liquids of phosphoric acid and sulfuric acid. To guaranteed polishing quality,some matters such as oxidant,organic macromolecule,surfactant,and heavy metallic salt must added in. These matters are very important of Chemical Polishing,they can enhance smoothness and brightness,avoid pitting corrosion. In fact,it's very difficult to decided which added matters were useful,we must do a great many of experiments.In this subject,we use orthogonal experimental to study the action of these added matters and there synergism. Finally,we confirmed which added matters were most useful and without sideeffect. Because some technological conditions are also contribute to polish quality,so we still studied the optimized conditions such as polish time and temperature.In our research we still analysis the process by SEM and mechanism by electrochemical method of this Chemical Polishing technique,this is the firsttime who use SEM to study Chemical Polishing process without yellow fume. After researched we considered that planing and brighting were occurd at the same time,mucouse coat theory and passivation theory can give explanation of polishing mechanism. In addition,to obtain the aluminum surface smooth and bright organic macromolecule adsorpted on the surface is bottleneck .This new polishing technique had overcome two chief deficiency of some Chemical Polishing methods without yellow fume,favorable of environment protection,and some manufactory were used this technique already. We think it can widely used in the future. Author:Hongtao Pang (Material Science) Directed by:Prof. An LinSenior Engineer,Xinqing Li...