Aluminum Flake Surface Multi-layer Coating Performance

As one kind of aluminium pigments, lamellar aluminium is widely used in the industry. However, the lamellar aluminium is easily corroded by acidic medium and get aggregate when exposed to the air for long time, which seriously impact its performance. Therefore, the surface treatment before devotion of production of aluminium pigments is necessary. It is effective to prevent lamellar from corrosion when coating thin layers on the surface of flake aluminium with inorganic oxide film. In the paper, the impact of multilayer-coating on the surface of lamellar aluminium to its performance was studied, which was divided into three steps: pre-treatment experiment, the preparation of SiO2/Al particles, and the preparation of TiO2/SiO2/Al particles.Furthermore, the theoretic analysis of the thickness of film and reflectivity were also researched.The pre-cleaning steps have been conducted to remove the impurities on the surface of original aluminium, and the effects of pre-treating time and the dosage of acetone were researched. The result showed the optimum pre-treating time was 3 h and the ratio of aluminium and acetone was 4 g:50 ml.With the Al particles with lamellar aluminium powder as the core, the silicon dioxide as film, SiO2/Al particles were prepared with tetraethyl orthosilicate (TEOS) as precursor by the sol-gel method. The effects of all the formulation factors:the sequence of catalyst adding and the coating times have been thoroughly investigated. The stability of the aluminium pigments in acid was examined by measuring the hydrogen generation. The coated aluminium pigments were characterized by IR, XRD, SEM-EDS and TEM.The specific surface and thermal stability were tested with BET test and TG analysis, respectively. Based on the test results, it is found that the sequence of catalyst adding would be first hydrochloride, then ammonia, three times coating samples had the best anticorrosive property.Base on the second step experiment, the home-made SiO2/Al particles was coated with a layer of TiO2 when titanium tetrabutoxide (TBT) acting as precursor, thus the TiO2/SiO2/Al compound particles were prepared.The effects of all the formulation factors:pH, V (TEOS): V(TBT),the calcination temperature and the dosage of surfactants have been thoroughly investigated. The stability of the coated aluminium pigments under different conditions in acid was examined by measuring the hydrogen generation. The similar methods of characterization as the last steps,such as IR analysis, XRD, SEM-EDS,BET test and TG analysis were used. The results showed that the sample owned the least evolution of hydrogen and get the best anticorrosive property under the condition of that:pH was 3,the V(TEOS):V(TBT) was 3:5,calcination temperature was 600℃,the concentration of surfactants was 0.07mol/L.A novel calculation model has been created to calculate the theoretic thickness of coated aluminium particles based on the experiments.The connection between coating thickness and coating conditions is explored through estimating the coating thickness. The variety of reflectivity of samples with SiO2 single-coating and TiO2/SiO2 double-coating were estimated respectively, which explores the effects of coating layers to reflectivity.