Copper Plating MIL-C-14550
Copper Plating has primarily been used as an under plate for nickel and chrome plating. It may also be used as a stop off for heat treating as a carburizing and decarburizing shield. Copper is also highly conductive, second only to silver. Seminole Metal Finishing does copper plating as an under plate and a final coating for conductivity followed by a chromate “bright dip” to keep the copper from turning.
Bright Dip on copper and brass alloys is an acid based chromate conversion coating used to protect and add shelf life to the base material.
The parts are first cleaned to remove any oil and dirt that may be on them from processing and manufacturing. After the parts are clean, the parts are processed through a chromate conversion coating. The film that forms adds shelf life and prolongs future tarnish and corrosion to the base material. It is not a permanent coating that will stop tarnish forever. However, a sprayed on coat of clear lacquer or polyurethane will further enhance the corrosion resistance of the bright dip.
Copper plate can also be used to “Stop Off” selected areas of a part which prevents carburization, decarburization, and nitriding in the plated areas. The picture below shows cams that have been copper plated to prevent the steel underneath from getting carbon introduced into it from the heat treat process and remain “softer” than the lobed cams, which were exposed to the heat treat.
After copper plating, these cams will be machined on just the lobes to remove some of the copper. Then the cams will be heat treated to harden the lobes but not the rest of the steel that is left copper plated.