Black inactivation process for zinc-nickel alloy coating

• Main Authors: WENJIANG DING, WENBIN HU, AIZHONG XU
• Format: Patent
• Language: English
• Published: 05.07.2000
• Edition: 6
• Subjects: CHEMICAL SURFACE TREATMENT; CHEMISTRY; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATIONOR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY IONIMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; COATING MATERIAL WITH METALLIC MATERIAL; COATING METALLIC MATERIAL; DIFFUSION TREATMENT OF METALLIC MATERIAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION INGENERAL; METALLURGY; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THESURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION

The black inactivation process of the present invention has low cost and less environmental pollution. It includes two steps, the first is pre-inactivation of soaking in solution containing nitric acid, sulfuric acid, chromic anhydride, sodium fluoride, etc. for 1-30 s, and the second is closed inactivation of soaking in solution of sodium dichromate at room temperature to 70 deg.c for 1-30 min. The black inactivating film is homogeneous, and the inactivated coating, test shows, has a no red rust period longer than 1000 hr in neutral salt fog. The black inactivating film has the main components including NiO, NiH2, chrome compound, etc. The present invention is suitable for the black inactivation of zinc-nickel alloy with nickel content of 8-20 wt%.