Brush plating

Abstract

The advantages and disadvantages of brush plating are listed. The advantages include an ability to touch up defective electroplated components, the possibility of plating in situ, a reduction in the cost of stopping off, the benefits of plating selected areas, the possibility of plating contaminated components, the ability to achieve good adhesion on certain “difficult” substrates, low hydrogen embrittlement and the possibility of repairing worn parts. The main disadvantages are that the operation is labour intensive, the proprietary solutions are expensive and a suitable material must be found to wrap the anode. In the experimental section the development of CoMo and CoW alloys for use on dies and moulds, particularly for hot-forging dies and cold-press tools, is described. Results are reported for the effects of applied voltage and variation in solution formulation on both cathode efficiency and deposit composition. Reasons for the preferred solution composition and operating conditions are given. Some results of industrial trials are tabulated and photographs are supplied to indicate the varying sizes of tools that have been plated on site or in the tool room. Brush-plating solutions have been developed that enable cobalt alloys containing about 6% Mo or 8% W to be deposited at 17–20 V from relatively simple acid electrolytes.