Guides / Choosing a Supplier
Questions to Ask a Plating or Coating Shop Before You Send Parts
October 11, 2026
A quote tells you a price and a lead time. It does not tell you whether the shop actually runs your process every week or is learning it on your parts, whether your part fits their equipment, or whether hardened steel gets the bake it needs. These questions get at that before the first lot ships, not after it comes back wrong.
Which specs do you run every week, not just occasionally?
A shop that lists a process on its website and a shop that runs it in volume every week are not the same thing. Ask directly how often they run the specific spec on your drawing, not just the general process. A shop running ASTM B841 zinc-nickel weekly has its bath chemistry, thickness control and paperwork already dialed in. A shop that ran it twice last year is starting closer to zero.
Can you show a sanitized certificate of conformance for this spec?
A certificate with the customer name removed shows what the shop actually records: spec, type, class, thickness readings and any test results. It is a better signal than a verbal assurance, because it shows the paperwork exists and matches what your own lot’s certificate would look like.
What is your largest tank, barrel load or line envelope?
Size limits decide more quotes than any other single factor. Give the shop your largest part’s dimensions and weight and ask plainly whether it fits, and how it will be held: barrel, rack or conveyor line. A shop that has to special-fixture your part or split a run across smaller batches is telling you something about cost and lead time before you even see a number.
How do you clean and activate this base material?
Most coating failures start before the coating, in the cleaning and activation steps. Ask specifically about your base material: how they remove heat treat scale from steel, how they activate aluminum or stainless before plating, and how they handle parts that arrive oily or rust preventive coated straight from storage. A shop that answers in general terms about “our process” without naming the steps for your specific material is worth a second question.
Can you bake hardened steel, and is it recorded on the certificate?
If any part is high strength steel, above roughly 39 HRC, this question separates shops that treat hydrogen embrittlement seriously from ones that do not. Ask how soon after plating the bake starts, what time and temperature they use for the hardness in question, and whether the bake is recorded on the certificate. A shop that has never been asked this is not necessarily a bad shop, but it is one you should confirm carefully before sending hardened parts. See hydrogen embrittlement and the relief bake for what the requirement should look like on your drawing.
What will you measure on each lot, and what comes back with it?
Get specific: thickness readings by what method, on how many parts and at which points, adhesion testing if applicable, salt spray results if required, and whether a certificate of conformance is standard or an added request. Paperwork agreed before the first lot is paperwork you actually receive; paperwork assumed and requested afterward often is not available.
What is your normal turnaround, and what happens at double the volume?
Most finishing processes themselves take days once parts are in house. The variable is queue time on a busy line, color changes on a powder line, and masking backlogs. Ask what a realistic turnaround looks like for your lot size specifically, and what changes if your order doubles, especially if you expect a repeating or growing order.
Do you run every process in-house, or send some out?
An assembly that needs two or three finishes is sometimes run entirely in-house and sometimes split across a shop and its own subcontractors. Neither is automatically wrong, but subcontracted steps add handling, transit time and a second set of paperwork to track. Ask plainly which processes happen on site.
How do you handle a lot that fails inspection?
Every shop has a rejected lot eventually. Ask what happens next: do they strip and rerun the parts, credit the cost, or expect you to absorb the failed lot as scrap. Ask how they figure out what went wrong before rerunning, rather than just repeating the same process and hoping for a different result.
A shop with a real answer, naming a process for root cause and rework, is telling you it has handled this before in a structured way. A shop that treats the question as unlikely to ever apply to them is telling you something too.
What happens if a mistake is found after the parts ship?
Parts sometimes leave a shop, get assembled, and only then reveal a thickness or adhesion problem during your own incoming inspection or a customer’s audit. Ask directly how the shop handles this: do they take returns, issue credit, or dispute the finding. This is a harder conversation to have for the first time after a real mistake than before one, so it is worth having early.
Putting it together
Send these questions with your first RFQ rather than after a quote comes back. A shop that answers all of them clearly, including the ones about tank size and bake timing, is worth a trial lot. A shop that skips the specific ones and stays general on process usually tells you something too. For the broader checklist of what a fit-for-purpose shop looks like, see how to choose a metal coating supplier.
How we help
We are a matching service, not a plating shop. Send one RFQ and we pass it to up to three finishing shops that already run your process, hold your spec and have equipment sized for your part, so these questions start from a stronger position. Go straight to the RFQ form or read the coating RFQ checklist first if you want the request itself to be complete.
See also how to check a finishing shop’s approvals.
See also what an ISO 9001 certificate covers for a finishing shop: ISO 9001 for a plating or anodizing shop.
Frequently asked questions
Should I ask these questions before or after getting a price quote?
Before, if the shop is new to you. A low price from a shop that cannot actually run your spec at your tank or line size is not a real quote yet. Confirm fit first, then compare price among shops that clear the bar.
Is it reasonable to ask a shop for a reference customer?
Reasonable to ask, but many shops cannot share customer names due to confidentiality agreements. A sanitized certificate of conformance, with the customer name removed, is usually something a shop can share and tells you more about actual process control anyway.
How many of these questions should a good shop be able to answer without hesitation?
Nearly all of them, for the processes they say they run. Hesitation on tank size or spec frequency is normal caution about giving exact numbers away from a competitor; hesitation on whether they can bake hardened steel or hold a spec at all is a different kind of answer.
What if a shop answers honestly that they do not run my spec, but offer to send it out?
That is a useful, honest answer, but it means a second shop and a second set of paperwork are now part of your supply chain. Ask who that subcontractor is and whether you can qualify them directly instead, especially for a repeating order.
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Send the drawing. We match you with up to 3 finishing shops that run your spec and reply within 24 business hours.
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