Comparative study on surface influence to outgassing performance of aluminum alloy

In order to systematically evaluate the surface influence on aluminum alloy's outgassing characteristics, 10-hours outgassing experiments of 5A06 and 2A12 with different roughness and cleanness were firstly tested and compared. Then measurements of the outgassing rate and desorption gas components were performed on 7075 and 6061 with and without anodic alumina coatings. Furthermore, the substrate microstructures, surface micro-morphologies and element compositions of anodized aluminum alloys were analyzed emphatically. The results revealed that the surface roughness, cleanliness and oxide film all have influence on the outgassing behavior of aluminum materials. It is observed that the rougher the surface is, the more gases are released. It is pointed out that the outgassing rate of aluminum alloy with anodizing is 1-2 orders of magnitude higher than that without, which is mainly reflected by the significant increase in water vapor and the emerging of hydrocarbons. Combining with a detailed material analysis, it is concluded that the outgassed water of anodic alumina alloy is more originated from its surface hydrated products formed during the sealing process, while the emitted hydrocarbons are largely related to the organic maters used in the dyeing procedure.