Chromium Zinc-aluminum Coating Formulation Process

With the whole environmental protection consciousness gradually enhancement, has pollutional chromium of dacroment coating the development space getting smaller. Because the dacroment handicraft has the outstanding corrosion resistance, therefore the main body of the article is studying the zinc aluminium coating of not containing chromium on dacroment' s basis.This article first introduced this technical origin, the development, the research present situation, the development forecast as well as the film characteristic, the application. Second introduced the experimental material, the equipment and the experiment technical process, and introduced the corresponding examination method to the film performance. Third introduced the compositions of coating solution and the operating condition to the coating performance influence. Finally, the structure of the coat and the element composition have been analyzed, meanwhile the mechanism of coating formation and corrosion resistance have been discussed preliminary by using SEM, EDS. The results as follows:1.By discussion that raw material zinc powder, aluminum powder' s form and amount, the corrosion resistance of coat prepared with flake powder was better than that prepared with grainy powder which was found. So the flake powder was used. The stickiness of coating solution, the corrosion resistance and adhesion of coat were considered, the zinc powdercontents is controlled ultimately in 200 - 320g/L. At the same time, for getting fairly good coating outward appearance and increasing the corrosion resistance,aluminum powder contents is controlled between 40-200g/L.2. Considered the metal powder' s dispersivity in coating solution and the solvent complete volatility degree when roasting,used the mixed solvent. The solvent proportion is:Dimethylbenzene:A%; Normal butyl alcohol:B%; Ethyl acetate:C%.3. The cementing agent of the experiment is epoxy resin and the silicon hydride union, the coating which has good adhesion and corrosion resistance. Its amount of used as follows: Epoxy resin:Ag/L;Silicon hydride:Bg/L.4. The experiment through to the temperature, the time of baking and the time of agitating discussion, the condition of baking and agitating as follows: The preliminary baking temperature: 120-150℃,Time:25-30min;The sintered solidification temperature:300±10℃,Time:30min;Stirring time:4-6h.5. The zinc aluminium coating is silver-white color, has the metallic luster. The experiment time of corrosion resistance for ammonium nitrate can reach 120 minutes and 1000 hours for salt fog without appearing rust. Meanwhile, the bond strength between coat and substrate is very well. The coat does not have the chromium completely, conforms to the environmental protestion requirement.6. The superficial appearance and the composition of coating were analysised by using SEM and EDS. Meanwhile, the mechanism of coat formation and corrosion resistance were deduced by using SEM and EDS. The mechansim of corrosion resistance mainly is following several ways:Screening effect of structure; Zinc and aluminum is consumed as the anode;The ferric substrate has been protected;Zinc oxide and aluminium oxide inactivation effect.