Finishes at a glance
| Finish | Applied to | Main purpose | Typical uses |
|---|---|---|---|
| Natural / bright | Brass | Clean, tumbled surface; no coating | Internal parts, parts plated later by the customer |
| Nickel | Brass, steel | Corrosion and wear resistance, prevents tarnish; base layer for chrome | Inserts, connectors, fittings |
| Tin | Brass, copper | Solderability and stable electrical contact | Terminals, cable lugs, busbar parts |
| Silver | Brass, copper | Lowest contact resistance for high-current joints | Switchgear contacts, high-current connectors |
| Chrome | Brass (over nickel) | Hard, bright decorative surface | Bath and sanitary fittings |
| Zinc with passivation | Steel | Sacrificial corrosion protection | Steel fasteners and brackets |
| Passivation | Stainless steel | Restores the protective oxide layer after machining | Stainless turned parts |
| Anodising | Aluminium | Hard, corrosion-resistant oxide layer, can be coloured | Aluminium housings and spacers |
Finishes for electrical parts
Electrical parts are usually tin or silver plated. Tin is economical and easy to solder or crimp. Silver gives the lowest contact resistance but tarnishes in air containing sulphur, so it is often given an anti-tarnish treatment. In some electronic uses, pure tin can grow fine whiskers over time; a nickel underlayer or a matte tin deposit is commonly specified to reduce this risk.
Compliance points
- Hexavalent chromium is restricted under RoHS and REACH. Zinc plating is normally finished with a trivalent passivate instead.
- If a salt spray test is required (for example a minimum number of hours to white or red rust), state the test standard and duration on the drawing.
- Ask for a RoHS / REACH declaration with the parts if your market requires one.
What to put on the drawing
- Finish type and, for plating, the thickness range in µm
- Which surfaces are significantPlating thickness is measured there; other surfaces may be thinner.
- Areas to mask or leave unplatedThreads and tight bores often need allowance, since plating adds thickness on every surface.
- AppearanceBright, satin or matte.
- Test requirementsThickness measurement, adhesion and salt spray, with the standard named.
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