Trivalent chromium electroplating baths and electroplating therefrom
AssigneeAlbright & Wilson Limited
InventorsJeffrey Gyllenspetz, Stanley Renton
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Abstract
It is known to attempt to plate chromium from a solution containing trivalent chromium salts and organic complexants. The invention provides an aqueous chromium electroplating system containing trivalent chromium, together with both a formate or acetate and a bromide. Optionally the solution also contains ammonium, borate, chloride, sulphate and alkali metal ions and a wetting agent. The invention has the advantage of providing a solution with commercially acceptable covering and throwing power whose effluent can easily be purified to acceptable standards.
Claims30
An aqueous acidic chromium electroplating solution which consists essentially of (a) from 0.1 to 1.2 molar trivalent chromium, (b) carboxylate selected from formate and acetate in a proportion of from 3:1 to 0.5:1 molar based on chromium, (c) bromide in a molar ratio of bromide to chromium of from 1:1 to 1:10, and at least 0.1 molar ammonium.
An aqueous acidic chromium plating solution consisting essentially of from 0.1 to 1.2 molar trivalent chromium;
- at least 0.01 molar bromide;
- formate in a molar ratio of formate to chromium from 3:1 to 0.5:1;
- at least 0.1 molar ammonium and at least 0.1 molar borate.
An aqueous acidic chromium electroplating solution consisting essentially of from 0.1 to 1.2 molar trivalent chromium;
- from 0.05 to 0.3 molar bromide;
- formate in a molar ratio of formate to chromium of from 2:1 to 1:1;
- from 1 to 3 molar ammonium;
- and from 0.5 to 1 molar borate.
An aqueous chromium plating solution consisting essentially of water, from 0.2 to 0.6 molar trivalent chromium, from 0.05 to 0.3 molar bromide, formate in a molar ratio of formate to chromium of from 2:1 to 1:1, from 1 to 3 molar ammonium, from 0.5 to 1 molar borate, from 2.5 to 3.5 molar of anion selected from chloride and sulphate amd having a pH between 1 and 4.
Dependencies are inferred from the claim text.