Indian brass suppliers offer nickel, chrome, tin and silver plating, along with natural, polished and passivated finishes. Each finish does a different job, so choose it for the function, not just the look.
Plating is often done by a separate plating unit, not the turning shop. That makes plating one of the main points where quality varies between lots.
What each finish is for
- Nickel plating gives a hard, bright or satin finish that resists tarnish. It is used on fittings, fasteners and decorative parts, and as an undercoat for chrome.
- Chrome plating is a thin layer over nickel. It gives the familiar bright, blue-white sanitary finish and adds scratch resistance.
- Tin plating protects electrical parts from tarnish and keeps them easy to solder and crimp. It is soft and wears quickly under repeated insertion.
- Silver plating gives the lowest contact resistance and is used on high-current contacts and switchgear parts. It tarnishes in air, which may need an anti-tarnish treatment.
- Natural or passivated brass is used where appearance does not matter and the part is protected in use.
How to specify plating
Write the plating type, the minimum local thickness in micrometres on significant surfaces, and the standard. Useful standards include ISO 1456 for nickel and chromium, ISO 2093 or ASTM B545 for tin, and ISO 4521 or ASTM B700 for silver.
Name the test method for thickness, such as X-ray fluorescence under ISO 3497. Name any adhesion and corrosion tests, such as a neutral salt spray test, explained in salt spray testing for plated parts.
Remember that plating adds thickness. On threads and tight fits, the drawing should say whether dimensions apply before or after plating.
Regulatory points
Nickel can cause skin allergy. The EU limits nickel release from articles in prolonged contact with skin under REACH. If your part touches skin, check with your test house whether this applies.
Some buyers ask for trivalent chrome processes because of restrictions on hexavalent chromium. Confirm the current rules for your market with your compliance adviser before you specify the process. As the importer, you are responsible for compliance.
Common plating problems
- Thin plating in recesses and bores, where current density is low.
- Peeling or blistering from poor cleaning before plating.
- Dull or stained patches from contaminated baths or poor rinsing.
- Tarnish in transit when parts are packed damp or without protection.
Controlling plating across lots
Ask your supplier which plating unit it uses, and whether the same unit will plate every lot. A change of plater is a change of process, so it should be agreed with you first.
Approve a reference sample for colour and finish, and keep one at each end. Ask for a thickness reading on a few parts from every lot, taken on the surfaces that matter. Parts should be dried fully and packed in sealed bags soon after plating.
Next step
We find and audit manufacturers and their plating units, check samples and have lots tested. To set plating checks that suit your parts, book a free sourcing review.