Selective Electroplating / Brush Electroplating
What is Selective Electroplating?
Selective Electroplating also known as Brush Electroplating, Selective Electroplating or Electro Chemical Metalizing is a metal/alloy deposition method for localised electroplating without using an immersion tank system. (See https://en.wikipedia.org/wiki/Electroplating)
The process utilises an electrical current to deposit a desired material from a solution and bond it to a conductive object. A thin layer of material such as a metal or an alloy can thus be deposited upon the substrate surface. Surfaces liable to be plated may vary from cm² to m². The deposit thickness ranges from a few microns to several tenths of a millimetre. (See Marlinec – Selective Electroplating.pdf)
Why use Selective Electroplating?
Selective Electroplating is primarily used for depositing a layer to bestow a desired property/characteristic to a surface that otherwise lacks that property.
Unique features of Selective Electroplating:
- It is fast
- Can deposit hard metals (Rockwell C50 and above) at 25µm/minute
- Can deposit soft metals at up to 250µm/minute
- It is ideal for dimensional restoration
- It is portable which makes it ideal for field repairs or on assemblies
- It has excellent bond strength exceeding 97MPa (> 14 000 PSI)
- A wide variety of metals, alloys and conversion coatings can be applied with the same equipment
Benefits
- Selective areas can be plated. No need for a tank system
- Excellent adhesion. Comply with numerous specifications throughout various industries
- No thermal distortion of any kind (cold process)
- Wear and abrasion resistance
- Excellent thickness control
- Portability – onsite / in situ
- Fast turnaround time
- Cost effective
- Dimensional restoration of original equipment manufacturer’s dimensions
- Practically no dimensional restriction to component size that can be plated
- Good corrosion resistance
- Good lubricity
- Exceptional hardness
- Defect repairs
- Anti-galling properties
- Aesthetic qualities
Selective Electroplating vs Other Repair Methods
| Criteria | Selective Electroplating | Welding | Metallizing | Electroplating |
|---|---|---|---|---|
| Precise Build-up Capability | Excellent | Poor | Poor | Fair to Good |
| Bond Quality | Excellent | Excellent | Fair to Good | Good |
| Thermal Distortion or Internal Stresses | None | Frequently | Sometimes | None |
| Density of Deposit (Porosity) | Very Dense* | Very dense but with blow holes | 70-90% theoretical density | Dense |
| Portability | Yes | Yes | Sometimes | No |
| Need for Post Repair Machining or Grinding | Not required on deposits up to 0.025mm. on smooth surface | Always required | Most always required | Usually required |
| Hydrogen Embrittlement | No* | No | No | No |
* Deposits are approximately 25% and 790% less porous than electroplated and metallized coatings respectively.
Plating Material Surface Hardness
| Plating Deposit | Rockwell / Vickers Hardness | Application |
| Cobalt Machinable | 40Rc | Heavy metal build-up particularly in the repair of over machined parts. |
| Copper (heavy build alkaline) | 21Rc | Fills pits and scores, repairs parts not subject to extreme heat or wear. |
| Nickel Acid High Build | 50Rc | Build-up of over machined parts subject to wear and/or heat. |
| Nickel High Speed | 46Rc | Build-up and resizing, worn or over machined parts. |
| Nickel Tungsten | 63Rc | Hard wear resistant finish over other deposits. |
| Nickel Cobalt | 43Rc | Build-up and resizing of parts subject to wear and above normal heat. |
| Cadmium | 15-20Hv | Used for corrosion protection of aircraft parts on ultra-high strength steel. |
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