Research On High Protective Anodic Oxide Composite Film Of Aluminum Alloy And In-situ Coupled Coloring

Aluminium anodizing oxide （AAO） film is a kind of porous ceramic film withexcellent wear resistance and corrosion resistance, which could be fabricated byanodizing the surface of aluminium alloy and be coloured with several coloringmethods to obtain colour film with good protective and decorative fuction. With theextensive uses of aluminum and alloy thereof in architecture, aviation and military,the requirements for the protective performance and decorative effect of AAO fiombecame much more stringent. Therefore, investigation of the AAO film and coloringtechnic was the hotpoint in this field.The main routes at present to improve the protective performance of AAO filmare hard anodic oxidation or composite anodic oxidation. Hard anodic oxidationcould form a compact hard oxide film with high hardness, high corrosion resistanceand high wear resistance on the surface of aluminum or alloy thereof by applyingdifferent oxidation electrolyte or changing the wave shape of power source. However,hard anodic oxidation films also give a poor mechanical strength and not easy topigment. Composite anodic oxidation is a kind of new route developed recently.When some insoluble powders such as Al2O3and TiO3were added into the oxidationsolution, the insoluble powder can be deposited on the film after electric reactionwith the oxidation film, which could improve the hardness, wear resistance andcorrosion resistance of oxidation film. Unfortunately, the composite anodic oxidationis not easy to be electrolytic colored twice. Generally, there are three colouringmethods for AAO film i.e. electrolytic colouring, chemical colouring and wholebody colouring. Films by electrolytic colouring have high corrosion resistance andlightfastness, but also show less varieties, dark tones and poor brilliance. Chemicalcolouring has the advantages of simple process, easy operation and brilliant colour,but the obtained film has poor lightfastness and weather resistance thus is notsuitable for use out-of-doors. The whole body colouring could obtain films withexcellent corrosion resistance, moisture resistance and lightfastness, but also has less varieties and poor brilliance, as well the high energy consumption. To improve theprotective performance and decorative effect, more research has emphasized on theprocess, reaction mechanism, structure and colouring routes of AAO film.When electrolytic mechanical route has been applied, several kinds ofnegatively charged silicon-containing superfine particle have been added toelectrolyte containing inorganic acid and organic acid to form a poroussilicon-containing composite AAO film on surface of aluminum or alloy. Accordingto the structure of AAO film obtained from different electrolyte such as inorganicacid, organic acid and alkali, the electrolyte composition and process technic tofabricate porous silicon-containing AAO film have been established. Furthermore,the structure and composition of AAO film have also been investigated. The resultsshow that the silicon contained in AAO film exists primarily of NaAlSi3O8withfeldspar structure. and the obtained composite AAO film gives apparent density of3.53g·cm^-3, porosity of10.6%and thickness of over20μm.In the systhsis process for dying agents, malonic acid diethyl ester was used andreact with aniline derivant to prepare several kinds of N,N’-diphenylmalondiamidederivant. N,N’-diphenylmalondiamide derivant could further react with substitutedbenzene diazonium salt resulting in nine kinds of azobenzeneN,N’-diphenylmalondiamide derivant of which seven kinds are new compound. Thefactors influencing the synthesis of N,N’-diphenylmalondiamide derivant andazobenzene N,N’-diphenylmalondiamide derivant have been investigated detailly.Furthermore, UV-Vis spectra, IR spectra, HNMR and MS have been used to analyzethe structure of products.When azobenzene N,N’-diphenylmalondiamide derivant was embedded into themicropores of silicon-containing composite AAO film by in situ coupling reaction, akind of composite colouring film with high lightfastness, excellent brilliance andabundant varieties can be obtained. According to the research on the relationbetween structure and preparation condition, the optimal technic condition has been established. To investigate the structure of synthesized dying material, the colouringfilm was stripped from the surface of aluminum by chemical method and dyingmaterial was then obtained by extraction method. According to the analysis byUV-Vis spectra, IR spectra, HNMR and MS, it is determined that the dying materialis azobenzene N,N’-diphenylmalondiamide derivantThe protective and decorative performance of silicon-containing compositecoloured AAO film has been investigated by a series of tests. After336h salt fog test,the grade of composite AAO film is level10. After ten period （240h） alternating hotand humid experiment, the composite AAO film gives no change. After28day（672h） mould test, the grade of composite AAO film is classified of level0. After1year （365day） physioclimate exposion test, the grade of composite AAO film isclassified of level10. Spectrum analysis results show that the reflect spectrum ofsilicon-containing composite AAO film is in line with the absorption spectrum ofcolorant in solution. Absoption is at λmax of380-480nm and the complementarycolours are yellow or yellow green, which is in accordance with visual inspection.Tests and analysises results show that, the coloured silicon-containingcomposite AAO film by in situ chemical reaction colouring method can meet thehigh requirement of protection at different stringent condition, such as humid,industrial gas contained, high salinity and dusted atmosphere. Furthermore,composite AAO film not only gives the high corosion resistance and lightfastnessequal to that of coloured film from electrolytic coloring method, but also shows theabundant varieties and bright colour equal to that of coloured film form chemicalcolouring method. Therefore, the in situ chemical reaction colouring method is aimportant progress of process and principle for high protective and decorativecomposite film on aluminum surface and will push forward the industrialdevelopment in this field significantly.