<P> Although anodizing produces a very regular and uniform coating, microscopic fissures in the coating can lead to corrosion . Further, the coating is susceptible to chemical dissolution in the presence of high - and low - pH chemistry, which results in stripping the coating and corrosion of the substrate . To combat this, various techniques have been developed either to reduce the number of fissures, to insert more chemically stable compounds into the oxide, or both . For instance, sulfuric - anodized articles are normally sealed, either through hydro - thermal sealing or precipitating sealing, to reduce porosity and interstitial pathways that allow corrosive ion exchange between the surface and the substrate . Precipitating seals enhance chemical stability but are less effective in eliminating ion exchange pathways . Most recently, new techniques to partially convert the amorphous oxide coating into more stable micro-crystalline compounds have been developed that have shown significant improvement based on shorter bond lengths . </P> <P> Some aluminium aircraft parts, architectural materials, and consumer products are anodized . Anodized aluminium can be found on MP3 players, smartphones, multi-tools, flashlights, cookware, cameras, sporting goods, firearms, window frames, roofs, in electrolytic capacitors, and on many other products both for corrosion resistance and the ability to retain dye . Although anodizing only has moderate wear resistance, the deeper pores can better retain a lubricating film than a smooth surface would . </P> <P> Anodized coatings have a much lower thermal conductivity and coefficient of linear expansion than aluminium . As a result, the coating will crack from thermal stress if exposed to temperatures above 80 ° C (353 K). The coating can crack, but it will not peel . The melting point of aluminium oxide is 2050 ° C (2323 K), much higher than pure aluminium's 658 ° C (931 K). This and the non-conductivity of aluminum oxide can make welding more difficult . </P> <P> In typical commercial aluminium anodizing processes, the aluminium oxide is grown down into the surface and out from the surface by equal amounts . So anodizing will increase the part dimensions on each surface by half the oxide thickness . For example, a coating that is 2 μm thick will increase the part dimensions by 1 μm per surface . If the part is anodized on all sides, then all linear dimensions will increase by the oxide thickness . Anodized aluminium surfaces are harder than aluminium but have low to moderate wear resistance, although this can be improved with thickness and sealing . </P>

The aluminium article is used as an anode in the anodising process