What is Brush Plating (Selective Electroplating)?

Brush or selective plating is a method of electroplating from concentrated plating solutions on selected area without immersion tanks. The solution is held in absorbent material wrapped around an anode.  Electrical contact is made by brushing or swabbing the part (cathode) with the anode. It is also called brush plating.  Faraday's laws of electrolysis applies to selective plating.  Faraday's Law

Benefits of Brush Plating (Selective Electroplating)

1. Prevent or minimize disassembly of workpiece
2. Portable equipment allows on-site work
3. Plate large parts or other parts not easily tank-plated
4. Supplement tank plating, minimize masking
5. Restore worn, corroded or mis-machined parts
6. Improve solderability, EMI shielding, conductivity in select areas

Brush Plating Equipment (selective)

1. DC Power Supply (Brush Plating Machines)
2. Anode and Anode Holder (Selective plating supplies)
3. Solutions or Chemicals (Selective plating chemicals)
4. Containing and Transferring

Compare to Tank Electroplating

1. Same electrochemical process as tank electroplating but a different method of application.
2. Brush plating chemicals are more concentrated
3. Brush plating uses higher current densities - faster build-up of metal deposit
4. The brush-plated deposit can be more dense, less porous
5. Precision build-up easier with brush plating
6. Brush plating equipment is portable. Click to view our Photo Gallery.

Brush Plating Machines

The basic features are a voltmeter, ammeter, variac, polarity switch, and circuit breaker. Additional features are an amp-hour meters and dual operating ranges.

Anode Assembly

An anode assembly consists of a handheld anode holder, an anode and anode wrapping. Various anode handles are available to accommodate specific applications. Anodes are usually made from a material inert to the plating solution. Materials such as graphite, stainless steel and 90%platinum/10%iridium are commonly used. Anode wrappings are used to hold the solution about the anode and provide insulation between the anode and cathode(workpiece). Common wrapping materials are cotton, dacron and scotchbrite. Sometimes sleeves of a similar material are placed over the anode wrapping.

Chemicals and Purpose

a. Cleaning - remove surface contaminants
b. Activating - activate or etch base material
c. Anodizing or chromate coating - optional surface treatment for aluminum, zinc and cadmium only
d. Pre-plating - deposit a pre-plate which increases adhesion or prevents intermetallic diffusion between build-up plate and the base material. Often nickel or copper pre-plates are used on aluminum, steel or brass.
e. Finish or build-up - deposit a final plate which imparts certain functional or decorative qualities to the base metal. Metals that may be deposited are cadmium, copper, gold, lead, nickel, silver, tin, zinc, rhodium, platinum and palladium.  Alloys such as tin-lead,  tin-zinc, nickel-zinc and Babbitt may also be deposited in varying alloy compositions.
f.  Blackening - surface treatment for steel, copper, nickel, silver and tin. Click here for info Blackening .

Containing, Transferring, Disposal

Usually trays, beakers, polypropylene bottles are used to contain chemicals during storage and use. Laboratory wash bottles are used for rinsing workpieces.  Chemicals are considered hazardous materials and should be disposed of in compliance with all local, state, and federal requirements. Persons using solutions should wear personal safety equipment such as eye safety glasses or goggles, rubber or nitrile gloves, and a rubber apron if necessary.  

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