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How to Choose a Metal Finishing Subcontractor

by | Oct 14, 2026 | Metal Finishing

Industrial metal finishing facility with plated metal components and a checklist of 12 questions for choosing a metal finishing subcontractor.

How to Choose a Metal Finishing Subcontractor: 12 Questions to Ask Before You Award the Job

A finish is usually the last thing done to a part before it ships. It is also the first thing a customer sees, and the first thing to fail when something goes wrong. Rust, peeling, coatings, and parts that are no longer fit after plating can all be traced back to the finishing step.

That is why a price comparison is not enough. A quote tells you what a job costs. It does not tell you how the shop runs, who checks the parts, or what happens when a part is unusually large. The twelve questions below help you find those answers before you award the work.

They are grouped by capability, quality, compliance, and delivery, so you can go straight to the area that worries you most. Each one also shows what a clear, specific reply looks like.

Questions About Capability

1. Which finishing processes do you offer?

Many jobs need more than one finish. A shop that covers several processes saves you from managing extra vendors. Peregrine Metal Finishing offers six:

Ask about the specific product, too. Peregrine’s black oxide is a room-temperature process called EPI Insta-Blak 333. It gives a non-bleed black finish with excellent corrosion resistance, and the finish can be painted over.

2. What part sizes and weights can you handle?

Never assume your part will fit. Ask for exact limits. At Peregrine, the most common work is industrial fittings and adapters from 8 oz up to 100 lbs. The limits go well beyond that:

  • The plating line takes parts up to 700 lbs.
  • The tank measures 85″ long, 22″ wide, and 48″ deep.

Sandblasting handles parts weighing up to 7,000 lbs, as long as the shop’s lift truck can unload them from your truck.

3. Do you understand my industry?

Experience in your field means fewer surprises. Peregrine was founded in 2016 by people with a long history in machining and manufacturing. The shop serves steel, marine & offshore, automotive, aerospace, oil and gas, and general manufacturing customers.

Its zinc-nickel plating on carbon steel parts is used in all industries, especially steel, automotive, defense,  oil and gas, and mining. Black oxide also goes to many industrial customers.

Questions About Quality

4. Who inspects the work?

You want a named role, not a vague promise. At Peregrine, Certified Master Surface Finishers monitor daily production and personally inspect all orders. A certified Master Surface Finisher also reviews and processes every job. A laboratory staffed by technicians with plating and quality management experience supports them.

5. How do you prove corrosion protection?

Ask for salt spray results. Numbers beat adjectives. For zinc-nickel plating, Peregrine reports these typical results:

  • About 1,000 hours before white rust
  • Over 1,400 hours before red rust
  • A target thickness of 0.0003″ to 0.0005″ (7.6 to 12.7 microns)

Also ask what thickness the shop aims for. The target tells you how carefully the process is controlled. Peregrine describes its zinc nickel finish as hard and “anti-scratch,” with protection during handling and assembly.

6. What standard do you follow for stainless steel passivation?

A good shop names the standard. Peregrine performs acid descaling and inspection after cleaning to ASTM A380-06.

7. How do you avoid cross-contamination?

This matters most in shot peening. If carbon shot touches stainless parts, rust can show up later. Peregrine uses a dedicated shot peening machine with stainless steel shot to peen stainless steel parts. Its tumble shot peen service covers both carbon and stainless steel components.

8. Which plating problems do you work to prevent?

Ask the shop to name the common failures. Peregrine lists four it aims to avoid:

  • White corrosion
  • Poor adhesion
  • Poor salt spray results that lead to early rust
  • Topcoat peel

Questions About Compliance and the Environment

9. Are your processes RoHS compliant?

If your parts ship into regulated markets, this is a yes or no question. All of Peregrine’s processes follow RoHS 3 guidelines. Zinc nickel plating also serves as a replacement for toxic plating applications like cadmium plating.

10. Which chromate do you use?

Chromate is the conversion coating applied after zinc-nickel plating. It helps protect against white rust. Peregrine uses only purple/blue trivalent chromate. It does not use hexavalent chromate, which OSHA has classified as a human carcinogen.

11. How do you manage water and air?

A clean shop is usually a well-run shop. Peregrine recycles up to 75% of the water used in its processes through a wastewater treatment center paired with a reverse osmosis system. Its facility also scrubs and ventilates 36,000 cubic feet of air per minute.

Questions About Delivery

12. What is your turnaround, and who handles logistics?

Late parts can stall your whole line. Ask for real timelines and find out who arranges transport. Peregrine offers next-day delivery and can help with trucking logistics, delivery, and pickup. Sandblasting turnaround is typically 2 to 3 days.

Choosing a metal finishing subcontractor comes down to evidence. Ask what processes the shop runs, what sizes it can handle, and who inspects the work. Ask for corrosion test numbers and the standards behind each process. Check compliance, chromate type, and environmental controls. Then confirm turnaround and transport.

A shop that answers all twelve questions with specifics is easier to trust. Peregrine Metal Finishing is ready to answer them for your parts. Send a request for quote with your part details and see how the answers compare.