COATED REFLECTIVE SURFACE AND METHOD OF MAKING SAME

摘要

1286717 Coating reflective metal surfaces ESQUIRE Inc 8 June 1970 [9 June 1969] 27505/70 Heading B2E [Also in Divisions C7 F4 and G2] A metallic reflective surface, preferably an Al surface of a reflector in a lamp fixture for lighting football stadiums and shopping centres, is protected while increasing its specularity by coating it with a hydrophilic colloid whilst anodising the surface, and crosslinking or complexing the colloid preferably by dissolving a cross-linking or complexing agent in the anodising bath, e.g. in an amount from 0.001 to 10% by weight. Examples of such agents are K 2 Cr 2 O 7 , chrome alum (Cr K sulphate), amines and their salts, alcohols such as polyvinyl alcohol, boric acid, polyurea and other urethane precursors, dimethylol urea, hexamethylene-tetramine, aldehydes such as formaldehyde and gluteraldehyde, Al sulphate, Cr O 3 , glyoxal carboxylic acids and esters. The colloid is preferably a water-soluble or -dispersible polar hydrophilic material having functional groups selected from carboxyl, amino, hydroxyl and ether groups, and alkali metal complexes; e.g. natural or synthetic resin selected from water-soluble gums, alkali metal carageenins and alginates, gelatin, alkali metal salts of acrylic acid or acrylamide polymers, polyvinyl pyrollidone, ether, acetate or chloride, copolymers of vinyl acetate, methylcellulose, casein or starch or derivative thereof, cellulose acetate phthalate, or carboxypolymethylene. The colloid solvent may be water, alcohol, ketone or other polar solvent such as acetonitrile, formamide, dimethylacetamide or tetrahydrofuran. Prior to anodising and coating, e.g. to form an Al oxide-colloidate or -gelatinate, the surface may be cleaned in NaOHNaF solution, electro-brightened in fluoboric acid solution, and desmutted in H 3 PO 4 -CrO 3 solution. The anodising bath preferably contains 15% H 2 SO 4 with the colloid and agent. The coating may be hot-water sealed with water containing a wetting agent and with the pH maintained between 5.5 and 6.5 with H 2 SO 4 or NaOH; the sealing solution may contain KH 2 PO 4 and CrO 3 .