Method of improving the resistance to thermal shock of hard anodized aluminium surfaces

摘要

1,139,013. Treating anodized aluminium to improve its resistance to thermal shock. C.W. FORESTEK. June 29, 1967 [July 13, 1966], No. 29998/ 67. Heading C7B. An anodically produced oxide coating from 0À001 to 0À008 inch thick on Al or Al alloy has its resistance to thermal shock, which might craze or crack it, improved by drying the anodized surface and heating the surface by a dry method at a rate of no more than 4À1‹F. per minute either (a) to a temperature of from 200‹ to 212‹ F., or (b) to a temperature T, which is from 150‹ F. to less than 200‹ F. and maintaining the surface at the temperature T for a time of at least SP2/SP/ 5 (200-T) minutes, and after the heating step (a) or (b) cooling the surface at the rate of no more than 4À1‹F. per minute to room temperature. The anodizing may be in sulphuric, oxalic or chromic acid. Specified Al alloys contain minor amounts of Mg and Cu. After heating and cooling the anodized surface as above, the surface may be heated to at least 400‹ F. in not less than 30 minutes and subsequently be allowed to cool. The heat-treated anodized surface may also be treated with perfluoro-carbon, e.g. (Registered Trade Mark) "Teflon" as described in Specification 1, 126, 748.