Saturday, July 26, 2008

Equipment for Copper Plating

Steel tanks lined with rubber or plastic are preferred for large acid copper baths, but glass fiber reinforced plastic tanks are used for small volumes of solution. Lining materials that are generally suitable for either the sulfate or the fluoborate bath are properly formulated natural hard rubber, neoprene rubber, polyethylene, or elasticized vinyl chloride polymers. Air lines can be made of hard rubber or polymerized vinylidine chloride. Special grades of carbon pipe and tubing make efficient heat exchangers or less expensive. Rubber or rubber lined filters are used for continuous filtration, but stainless steel is satisfactory for short periods. Graphite is recommended for use as heat exchanger for copper fluoborate solution.

Preparation of Basis Metals
Because loose, nonadherent displacement films of copper are formed on steel and zink when these bases metals are immersed in acid copper baths, a cyanide copper or nickel strike plate is required before plating in acid baths. If the bases metal is completely covered, the strike plate can be as thin as 1.3 μm, 2.5 μm is sometimes preferred for parts of complex shape. After plating in the cyanide bath, the work should be thoroughly rinsed, dipped in a dilute solution of hydrochloric or sulfuric acid to neutralize any undissolved alkaline material, and rinsed again before plating in the acid bath.

Nickel or nickel alloys, when appropriately surface activated by cathodic treatment, reverse current etching in sulfuric acid, or other method, can be plated directly in an acid copper bath. Contact should be made to the work before immersion. Stainless and chromium steels are plated in acid baths with adherent copper deposits by first striking in a solution concentrated in sulfuric acid but dilute in copper sulfate 240 g/l sulfuric acid 112 g/l CuSO4.5H2O.
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