| 摘要 |
891,564. Multi-coatings of chromium and nickel. UDYLITE RESEARCH CORPORATION. Feb. 24, 1960 [Feb. 24, 1959], No. 6528/60. Addition to 855,695. Class 41. A metal surface is plated electrolytically with superposed layers of metal (1) a first coat of chromium 0.25 to 0.51 Á thick; (2) a coating of 2.5 Á or less containing cobalt which may be a flash coating of Co, Ni or an alloy thereof followed by (3) a plating with Ni or Ni/Co alloy containing up to 50% of Ni, the total layers 2 and 3 containing cobalt, being 5.1 to 51 Á thick; (4) a top plate of chromium 0.13 to 2.5 Á thick. Underneath this laminar coat, the metal surface which may be e.g. steel, zing alloy, or aluminium may be pre-coated with Zn, Cu, Cr, brass or Ni. The first chromium plate may be treated with H2O2, oxalic acid, dextrose or other agents to reduce any hexavalent chromium to tri-valent; the rinsing bath may have ultrasonic vibrations applied. The nickel plating and/or cobalt plating baths specified include a range of brightening agents including coumarin, bromal, sulphonamides and unsaturated aliphatic compounds. Aluminium surfaces may be anodised using H3PO4 before plating. |
