Barrel plating

Zn) penny with a less expensive copper-plated penny made from zinc strip (Zn—0.8% Cu alloy) (133,134). Zinc blanks stamped from the Hazelett-cast roUed zinc are barrel-plated with copper prior to coining to produce the finished penny. In 1992, about 22,000 Mt of special high grade zinc were used to make 9.1 biUion pennies. 

Current densities from 100—200 A/m are used for barrel plating. 

The future of cadmium plating is in question because of cadmium toxicity (83). Cyanide-free cadmium plating systems have experienced some growth. Acid cadmium, based on cadmium sulfate compositions, is replacing some cyanide baths in the United States. The fluoborate cadmium is reported in use in the UK, especially in barrel plating (84). Cadmium plating is covered by ASTM (85), U.S. government, and ISO specifications (86). 

Barrel plating of parts in copper cyanide solutions utilizes various formulations, some weaker, some stronger than the high speed baths. When plating parts that tend to stick together or nest during the barrel rotation, the free cyanide may need to be increased. This may require 35—40 g/L free potassium cyanide or more with an equal copper content. 

Titratable CN is less than total and is used to control bath. Barrel plating solutions are operated at higher CN and Zn levels. 

Doubling the concentration of the chemicals, except the hrightener, permits higher currents, up to 700 A/m for barrel plating and heavy buildup. 

Features of the method The solutions and prodecures are uncomplicated, and can often be adapted for barrel plating. Addition agents are usually necessary in order to restrict the high initial rate of plating, which might... 

For barrel plating, solution concentrations towards the maximum are recommended... 

In barrel plating, the barrel should be rotated for a time just above the plating tank in order to reduce the volume of dragged-out chemical. Holes in the barrels should be as large as possible to improve solution drainage while still containing the pieces. A fog spray directed at the barrel or its... 

Addition agents for all three plating solutions are as required, k Some baths contain 20—30 g/L NaBF4 and 20—30 g/L H3B03 instead of NH4BF4. C Current densities from 100—200 A/m2 are used for barrel plating. 

Plastic parts can be post-finished in a number of ways. Film and sheet can be post-embossed with textures and letterpress, gravure, or silk screening can print them. Rigid plastic molded parts can be painted or they can be given a metallic surface by such techniques as metallizing, barrel plating, or electroplating. Another popular method is hot... 

Mass plating is used for small workpieces to be plated in large quantities, such as nuts and bolts, but it is not used for delicate workpieces. The most widely used mass plating system is called barrel plating, where the work-pieces are loaded into a plating barrel. Other mass plating containers include plating bells and vibratory units. 

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