Hard anodised aluminium alloy pistons - especially for aero:modelling engines

摘要

The pistons are coated with a layer of anhydrous alumina, pref. a 50-600 microns thick hard anodised layer formed by bulk anodising by complete immersion in an anodising bath after final machining. The pistons are esp. useful for high speed (12000-20000 rpm) miniature engines, used in aeromodelling, and have increased wear resistance and thermal shock resistance. The layer has a hardness of 7-8 Moh's scale (500-800 HV), resists oxidn. in solns. of pH 6-9, has a m.pt. of 2100 deg.C and a thermal conductivity 10-65 times lower than that of aluminium.