Brush Plating Process

The LDC Process...

is brush plating. Brush plating is an Electrochemical Process specifically designed to be a portable and versatile method of electroplating, as well as anodizing or electropolishing, on localized areas and does not require immersing the part in large tanks of chemicals.

The basics of brush plating were developed in France about 1938...since 1978, Liquid Development Company (LDC) has been improving and developing this technology, while expanding its scope of applications.

How it works

The LDC Process of Brush Electroplating is quite simple in theory. A lightweight portable power pack is used to supply the direct current used in the process. This power pack will have two output leads, one (negatively charged), will be connected to the part requiring work, the other lead (positively charged), will be connected to the plating tool.

The plating tool, consists of a handle and an electrode (anode) which is wrapped with a cover. The operator mist then soak the plating tool with plating solution, either by dipping the anode into the solution or pumping the solution to the anode. The plating tool is then rubbed or "brushed" against the surface of the part being treated.

With all the components in place, the electrical circuit is completeed when the plating tool is touching the work surface, only then does the process actually begin. At this time, metal ions from the plating solution, will be deposited on the part and become bonded. To achieve a high quality finish, there must be a constant and uniform motion between the part and the plating tool, whenever they are in contact.

LDC Process Advantages

  • Portable - equipment can be moved to the jobsite
  • Excellent adhesion to most commonly used base materials
  • Minimize component disassembly - plate the part while still in place
  • Capable of rapid metal deposition rates - about 50 times faster than bath electroplating
  • Reduces the extensive masking and fixturing required, when compared to bath electroplating
  • Permits plating of parts thatare too large for normal plating baths
  • Minimize equipment downtime - keep the part in house and plate it on your schedule.
  • Ability to add metal without thermal distortion of base material
  • Minimize Hydrogen Embrittlement
  • Eliminate shipping costs - bring the plating to the part
  • Precise deposit thickness control, thus reducing or eliminating the need for post plating machining
  • Improves your company's financial bottom line - taking into account all the other advantages
  • Return on investment - generally less than 12 months

Frequently Asked Questions

1. What is Electroplating?
Electroplating is a process commonly known as Electrolysis. Electrolysis producing a chemical change by passing an electrical current through to the electrolyte (solution). The ions migrating to the electrodes, the positive ions which are the metal being deposited are attracted to the negative charged electrode (the part being plated). The negative ions are attracted to the positive electrode (Anode) and given off as gases.

2. What is Brush Plating?
The theory of brush plating is very basic. The part to be plated is given a negative (-) charge through a flexible wire lead from a special D.C. power pack. The plating tool or "brush" is positively (+) charged from the same power pack by a second insulated flexible lead. The plating tool assembly consists of an insulated handle with a graphite or stainless steel anode. The anode is covered with an absorbent material such as Dacron felt. The plating tool is then dipped into the desired plating solution and rubbed over the area where the coating is desired the plating only takes place where the anode contacts the part. The operator must maintain movement between the anode and the part to insure sound metal deposits.

3. What Advantages does Brush Plating Have?
Portability, Ease of operation, Rapid metal build up, Disassemble of machines, Plating of larger parts that won't fit in a tank, Excellent Adhesion, Dense coatings, No thermal distortion, Minimize hydrogen Embrittlement and reduces waste.

4. What is the meaning of Selective Plating?
Selective plating means that you can selectively plate an area by the means of masking off areas that need not be plated with either masking tapes or masking paints. Just like painting the material on. The job becomes the canvas or Cathode and the brush is the Anode and the paint is the metal.

5. Has Brush plating the same approvals as tank plating?
Brush plating is approved to many standards. Brush plating has many of its own approvals and these can be supplied from LDC on request. Many marine, electrical, aircraft and military bodies approve brush plating. (Blue folder containing all approvals)

6. Is it permanent?
Yes, Selective Plating is exactly the same as tank plating but much faster to lay down and has bond strength as good as the base metal if the process is used correctly.

7. How thick can you Plate?
Thickness is no problem but the costs are. In brush plating any thickness can be achieved by plating until the recommended thickness by LDC solution data sheets is achieved then the area must be smoothed off and re activated and plating carried out again. With harder materials it is common practice to lay a sandwich layer (i.e. Copper base with a hard nickel cap) this is far the cheapest way to lay a heavy thickness. (Manual Pages 249-250)

8. Can ID & OD areas be plated as well as flat areas?
Yes all areas can be plated with the LDC Selective brush plating. Spun bearings are a common repair on Shafts or Gear Box housings and are ideally suited to brush plating. Using some type of turning head or lathe to rotate the shaft or spindle or using an ID plater unit to plate Gear box ID's. (Manual Page 68)

9. Can tank-plating solutions be used for brush plating?
No. The content of brush plating solutions have a much higher content of metal than tank plating. If tank-plating solutions were used then a powdery deposit would be achieved.

10. Can Brush plating be done anywhere?
Yes this is called IN SITUE PLATING. The equipment can be transported anywhere. The metal is in the solution and the only other item needed is single-phase electricity. If larger deposits are needed then 3-phase power is needed and some kind of mechanical finishing might be necessary.

11. Can a Hard Chrome deposit be plated?
LDC is the only company that has hard chrome. The problem is that it takes a long time to lay down approximately 10 times longer than nickel and is expensive in both time and material. Hard chrome can be plated with other materials if needed such as Nickel Cobalt.

12. Can threads be plated?
This is called anti-gailing. Brush plating can be used for this purpose but it must be stressed, the throwing power must be considered on each application. Copper is the most commonly used material.

13. Can all metal materials be plated on?
Most materials can be plated on as long as they are not a base material such as steel and stainless steel. Base materials can be plated on but not plated. LDC has nearly a hundred solutions and a good selection of each material.

14. Can brush-plating materials be plated on Two or More Base Metals?
Yes, unlike tank plating brush plating has the capability of plating on two base metals because of the activating processes that can be changed to suit different materials.

15. What hardness can be achieved with brush plating?
This depends on the solution being used. LDC has hard chrome that is approx 70 Rockwell, Nickels at 48, 54 Rockwell, and Rhodium at 64 Rockwell and Nickel tungsten at 58 Rockwell.


16. Has LDC any Wear Resistant Materials?
LDC has a number of good wear resident materials. Chrome, Nickel, Nickel Cobalt, Cobalt-Tungsten, Nickel Tungsten, Rhodium. Etc

17. Is brush plating used for corrosion protection?
Many of the brush plating solutions and applications are used for corrosion protection. The main material is Nickel, Copper, Zinc, Tin and Cadmium

18. Does brush plating cause hydrogen embrittment?
The LDC brush plating procedures have been approved by aircraft manufactures to stop hydrogen embrittment and LDC has manufactured solutions that will not cause this such as cadmium NO-Bake. Cadmium S LDC-4803

19. Can you Brush Plate on Aluminum?
Yes brush-plating solutions are used very much for this purpose mostly with nickel for better soldering and brazing.

20. Can you Brush Plate to a Certain Thickness?
Yes, brush-plating can be worked out to plate a certain thickness and the power packs can be set to turn off all plating at that time.

21. Has LDC any High Temperature Materials?
A number of the solutions can be used in the high temperature range Chrome 1888c, Cobalt 1493c, Nickels 1454c, Palladium 1552c, and Coppers 1082c.

22. Can Hydraulic Rams or Spears be repaired with Brush Plating?
Hydraulic rams are a big part of the brush plating service because the plating can be brought to the ram rather than the ram going to the platers. Hard Chrome or nickel and nickel cobalt are used for this purpose after the damage has been filled with copper.

23. If Rams can be repaired then can Print Cylinders be repaired in situe?
Yes again this is a big part the service provided by brush platers. Same process as hydraulic rams this saves many hours of down time for the printing companies.

24. Do you have to Finish Brush Plating after plating has been carried out?
This depends on the finish required. If a large amount of plating is carried out then finishing will be required. If a very small amount of plating is laid down and the previous surface is good then no finishing is required.

25. What kind of finishing can be carried out after plating has been carried out?
This depends on the material used. Copper and soft materials like tin can be machined easily on lathes Etc. Nickel and Nickel based materials need to be ground using plenty of coolant. On some occasions a copper base is put down machined on lathes Etc. and a hard capping is put over the top. This is called a sandwich coating. Some bearing retainer diameters need not have capping as the copper is as hard on compression as the base material EG Mild Steel. Print cylinder and Hydraulic repair is usually finished by hand.

26. Has LDC any White metal bearing solutions?
The white metal solution is called Babbitt and is an excellent bearing material manly used on aircraft.

27. Can Needle-Bearing diameters be plated?
Needle bearing diameters can be plated but is a very hard process and much care must be taken. Nickel Cobalt is a very dense material and is suitable for this application.

28. Can Bearing Diameters be plated in copper and then capped?
Yes copper is as hard as steel on compression up to 65000 tons per sq inch so capping is not necessary but for visual and cosmetic purposes it can be done.

29. What advantages does Brush Plating have over welding?
Both welding and Brush plating has their advantages. Brush plating has one very good advantage is that no heat at all is needed. The solution heats itself sometimes and some solutions need heating for better density and adhesion but you can always place your hand on the item being plated. We say if you can weld then weld its cheaper and quicker but if you cant then come and see us.

30. Are their any Safety issues in using LDC Solutions?
All LDC operators are trained at special training centers and should know the safety procedures needed to carry out plating. Some of the solutions are acid based so precautions must be observed.

31. Can an Unknown base material be found with LDC Solutions?
Yes, by using solutions LDC-02 or LDC-04 in Reverse, then by looking in the wrap material a color will be observed. Magnetic test can also be carried out as well.

32. Can anybody carry out Brush Plating?
NO. All LDC operators are trained at special training centers and know how calculations and laid down procedures are carried out. At the end of all training classes test are conducted and only passes will be given operators certificates. If un-trained operators try this process then failures will occur.

33. Why use Copper as a defect repair Filler and is it hard enough?
Copper is used as a filler because it is always overstated about the yield strength needed for compression. If you take copper filling solutions Brinnell Hardness of approx 134 times this by 500 and you will get Compressive Yield Strength (PSI) so this example gives a 67000 PSI. "O" ring seal strength is approx 2000 PSI.

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