| 摘要 |
1,251,314. Electroless Ni coating of Al. UNITED STATES ATOMIC ENERGY COMMISSION. March 9, 1970 [April 2, 1969], No.11090/70. Heading C7F. Prior to electroless Ni coating, Al and Al alloy substrates are pre-treated in the following sequence of steps: (a) alkaline etch e.g. in NaOH or KOH. (b) etched in acid solution of NiCl 2 containing HNO 3 or lactic acid and treating with HNO 3 if the etching solution contains lactic acid. (c) de-smut with solution of HNO 3 / HF. (d) actuate with alkaline solution containing hypophosphite ion. (e) Depositing Ni strike coat by treating with aqueous solution containing Ni and hypophosphite ions and a chelating agent at 85-90‹C. and pH 9-9.5. Solution (b) may contain lactic or nitric acid and when lactic acid is used the Ni deposit is removed by treating with HNO 3 prior to desmutting. Solution (d) may contain 5-100 g/l hypophosphite ion and 5-50 mls/1 NH 4 OH. Solution (e) may contain 5-75 gms/1 Na or K hypophosphite, 5-60 gms/1 nickel sulphate and a chelating agent such as ammonium citrate, aminopolycarboxylic acids and their alkaline salts. The final Ni electroless coating bath is free of halogens. |
