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Fasteners, stampings, machined parts, enclosures, contacts
Metal finishing applications by industry and part type
The same finish is specified differently on a bolt, a busbar and a surgical instrument. This page lists the finishes each kind of part usually gets, the specs buyers call out and the detail that decides the quote. Send one RFQ and we match it with up to 3 shops that already finish parts like yours.
Finishes by industry
Typical combinations, not promised. Your drawing, its spec and the process control of the shop decide the result.
| Application | Typical parts | Common finishes | Specs often called out | What to watch |
|---|---|---|---|---|
| Fasteners | Screws, bolts, nuts, washers, pins | Barrel zinc, zinc-nickel, zinc flake, phosphate and oil, black oxide | ASTM B633, ASTM F1941, ISO 10683, OEM specs | Thread allowance, torque and friction coefficient, bake on high strength grades |
| Stamped parts | Brackets, clips, shields, springs | Barrel or rack zinc, zinc-nickel, e-coat, powder coat, tin | ASTM B633, ASTM B841, customer paint spec | Flat parts nesting in the barrel, bake for spring steel, cut edges on pre-coated stock |
| Machined parts | Housings, manifolds, shafts, fittings | Anodize, hard anodize, electroless nickel, passivation, black oxide | MIL-PRF-8625, ASTM B733, ASTM A967 | Build-up in bores and threads, masking of sealing faces |
| Hydraulics | Fittings, valve bodies, rods, cylinders | Zinc-nickel, electroless nickel, hard chrome then grind | ASTM B841, ASTM B733, AMS 2460 | Trivalent passivate on zinc-nickel, chrome thickness after grinding |
| Enclosures | Sheet metal boxes, panels, chassis, cabinets | Powder coat over phosphate or chem film, e-coat, zinc | Customer powder spec, AAMA 2603 to 2605, MIL-DTL-5541 | Masked ground points and threads, color and gloss reference |
| Automotive | Fasteners, brackets, brake and fuel parts | Zinc-nickel, zinc flake, e-coat | OEM corrosion and finish specs | PPAP documents, salt spray target named by the OEM spec, hex chrome free finishes |
| Electronics | Contacts, busbars, heat sinks, connector shells | Tin, silver, gold over nickel, electroless nickel, chem film | ASTM B545, ASTM B700, ASTM B488, MIL-DTL-5541 Class 3 | Minimum thickness at the contact area, solderability, tin whisker mitigation |
| Medical devices | Instruments, device housings, brackets | Passivation, electropolish, anodize, PVD | ASTM A967, ASTM B912, MIL-PRF-8625 | Cleanliness, lot traceability, biocompatibility stays with the device maker |
| Aerospace and defense | Fasteners, fittings, housings, landing gear parts | Zinc-nickel, IVD aluminum, chem film, anodize, passivation | AMS, MIL and prime contractor specs | Process approvals by the prime, test coupons and certs per lot |
| Food equipment | Machine guards, frames, conveyor and filler parts | Passivation, electropolish, electroless nickel, food grade powder | Rules of the destination market for food contact | Which surfaces touch food, cleaning chemicals the coating must survive |
| Architectural hardware | Handles, rails, exterior fittings, panels | Powder coat, anodize, PVD color, hot dip galvanizing | AAMA 2603 to 2605, ASTM A123 (galvanizing) | Color match across lots, outdoor UV and salt exposure class |
Hardened steel over 39 HRC
High strength fasteners, springs and heat treated parts over about 39 HRC need a hydrogen embrittlement relief bake after any electroplating, for example to ASTM B850, or a finish without hydrogen such as zinc flake. See the relief bake guide.
Finishes by part feature
Most problems show up at features, not on the flat surfaces. Mark these on the drawing so every shop quotes the same masking and build-up.
| Feature | What happens | What to specify |
|---|---|---|
| External threads | Plating builds on the flanks and can stop the nut | Thread class before or after plating, or a thin finish. Thread allowance guide |
| Tapped holes and bores | Electroplate is thin deep inside, powder does not enter, anodize grows into the wall | Mask, or size before finish; electroless nickel for even build |
| Grounding points | Anodize and powder insulate | Masked areas, or chem film Class 3 for conductivity |
| Sliding and wear faces | Soft finishes wear through | Hard anodize, hard chrome or electroless nickel with hardness. Wear surface guide |
| Cosmetic faces | Rack marks, color shift between lots | Rack point location, color and gloss sample, A and B surfaces |
| Electrical contacts | Thin or porous plating fails early | Minimum thickness at the contact zone, underplate |
| Sealing faces and fits | Build-up changes the fit | Mask, or give the dimension after finish. Masking guide |
Typical behavior, not promised. Background on corrosion testing: salt spray test.
Paperwork by industry
Ask for it on the RFQ, not after the order. It changes which shops can quote and the price.
- AutomotivePPAP level, control plan, OEM finish spec approval where the OEM requires it.
- AerospaceCertificate of conformance per lot, test coupons, process approval by the prime contractor.
- MedicalLot traceability, cleaning and passivation records, validated process where your quality system asks.
- FastenersBake records with time and temperature, thickness readings, friction or torque test results.
- ElectronicsThickness readings by XRF at the contact zone, RoHS and REACH declarations.
Guides by application
Deeper reading on single industries.
- Automotive fastener coatings
- Plating for electrical contacts
- Finishes for medical device parts
- Cadmium replacement for aerospace
- Outdoor powder coating for enclosures
- Coatings for food equipment parts
By base metal: finishing by base material. By finish: all finishes and specs.
Questions about applications
For how matching works, see the home page.
Why does the industry change who can quote my part?
Each industry brings paperwork as well as a finish: PPAP for automotive, process approvals and test coupons for aerospace, traceability for medical. A shop that does not work that way cannot quote the job even if it runs the finish. Name the industry and the paperwork on the RFQ and we match it with up to 3 shops that already work to it.
Do you recommend hexavalent chrome finishes?
Not as a default. Hexavalent chromium is restricted in many markets and by many OEMs, and trivalent passivates, trivalent chem films and zinc-nickel cover most of the same uses. If your drawing still calls for a hexavalent finish, say so on the RFQ, since fewer shops still run it.
Who decides the salt spray hours for my part?
You do, through the spec on your drawing or your customer spec. The finish, its thickness and the passivate or topcoat decide how a part performs in a test such as ASTM B117, and shops quote against the target you name. Ask for test results on coupons or parts from your own lot if the hours matter.
Can one shop finish all the parts of my assembly?
Sometimes. Many shops run one family of finishes, for example plating or anodize or powder coat. If your assembly needs several finishes on several base metals, list each part on the RFQ. We match shops that cover the set, or tell you where it has to be split.
One RFQ, up to 3 matched shops
Free for buyers. Send the drawing, base material, finish, spec, industry paperwork and lot size. We reply within 24 business hours with matched shops or a clear no.
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