Patent ID: 11926899
Assignee: RAYTHEON COMPANY
Field: Surface technology, coating (Chemistry)
Classification: CPC C | IPC C

Claim 12:
13. A process for coating a surface of an aluminum containing material, comprising:
degreasing a surface of an aluminum containing material in an immersion tank for 5-10 minutes at a pH of 9-11 and temperature of 110-150 F (43-66 C) to produce a degreased surface;
treating the degreased surface in a high alkaline treatment immersion tank immediately subsequent to the degreasing for 30 seconds-3 minutes at a temperature of 135-150 F (57-66 C), with a pH greater than 12 to produce an alkaline treated surface having smut on the surface; and
treating the alkaline treated surface with a hydrothermal treatment immediately subsequent to the high alkaline treatment for 20-60 minutes, wherein smut from the high alkaline treatment is not removed and the aluminum alkaline treated surface having smut on the surface is directly subjected to the hydrothermal treatment immersion providing the surface of the aluminum containing material with a chromate-free coating, wherein the highly alkaline solution in the high alkaline treatment immersion tank contains 15-60 g/l sodium hydroxide (NaOH), 5-20 g/l sodium bicarbonate (NaHCO3), 5-10 g/l sodium nitrate (NaNO3) with sodium sulfide (Na2S), triethanolamine (C6H15NO3) and potassium gluconate (C6H11KO7) and the high alkaline treatment immersion forms the smut which are oxyhydroxides of the aluminum and other metals present in aluminum containing material, wherein the oxyhydroxides comprise one or more of NaAl(OH)4, Al(OH)3, Mg(OH)2, Cu(OH)2, Cu2O, CuO, Cu2S, Na2Zn(OH)4, SiO2.xH2O.