What to Put on a Coating RFQ: Spec, Thickness, Masking and Racking

September 25, 2026

A plating or coating quote is only as good as the RFQ behind it. Shops price what they can see. Leave out the spec, the masking or whether a dimension applies before or after the finish, and you get a quote built on an assumption, or three quotes that cannot be compared because each shop assumed something different.

This checklist covers the fields that move a plating or coating quote the most, roughly in the order a shop reads them.

Base material and condition

Start with the alloy, not just “steel” or “aluminum”. 4140 and 1018 clean and plate differently. 6061 and 2024 anodize to different colors. Add:

Temper or heat treat condition, and hardness if it has been heat treated.
Cast or wrought. Castings often need extra cleaning and can show porosity after plating.
Any scale, plating or paint already on the part, if it is a rework or a repair.

If any surface is above roughly 39 HRC, say so. Electroplating and some cleaning steps can put hydrogen into high strength steel, and the shop needs to plan a relief bake, not find out at final inspection.

Finish, spec, type and class

Give the spec, not only the finish name. A short line per finish is usually enough:

Zinc plating: ASTM B633, type and class (for example Fe/Zn 8 Type III).
Zinc-nickel: ASTM B841 or AMS 2417, class and minimum thickness.
Electroless nickel: ASTM B733 or AMS 2404, service condition or phosphorus range.
Anodize: MIL-PRF-8625, type (II or III), class (dyed or undyed) and color if dyed.
Passivation: ASTM A967 or AMS 2700, and the test method if your customer specifies one.
Powder coat: color by RAL or sample, gloss level, and any performance spec such as AAMA 2604.

Anodizing-only items are in the anodizing RFQ checklist.

If you are still choosing between finishes, the finish comparison guide walks through which one fits which job before you write the spec line.

Thickness and where it is measured

State a minimum, or a range, not just a target. “20 µm” reads differently to different shops; “15 to 25 µm, minimum on significant surfaces” does not. Name the significant surfaces if the part is not simple, since thickness on a flat face and inside a blind hole are rarely the same number.

Say how thickness will be checked: magnetic induction and eddy current are common and nondestructive; XRF suits precious metal and thin films; cross-section is destructive and usually reserved for first article or dispute. If your customer’s spec names a method, put it on the RFQ.

Dimensions before or after finish

This is the field most often left blank, and it is the one that causes the most rework. Threads, bores, pins and any press or slip fit change size with plating or anodize thickness. State plainly which numbers on the drawing apply before the finish and which apply after it.

For threads, say whether the thread gauge applies before or after plating, and whether the shop should chase threads after a thick finish. For hard anodize, remember that roughly half the oxide grows outward and half penetrates the aluminum, so a bore sized for the bare part will not be the bore size after anodize.

Masking map

Circle every area that must stay bare, take a thin film only, or is fine with the full finish, and write which one applies. Threads, precision bores, bearing seats, ground contacts and gasket faces are the usual candidates.

Masking is hand work, so an unmarked drawing gets quoted with the shop’s own assumption about what needs protecting, and that assumption is often wrong in a way that only shows up when parts come back. Confirming masking in writing, line by line, is one of the fastest ways to make two quotes for the same part actually comparable.

Racking and contact points

Tell the shop how you expect the part to be handled: barrel for small parts in bulk, rack for larger or cosmetic parts, or a conveyor line for powder coat and e-coat. If the part is cosmetic, mark an acceptable spot for the rack or hook contact mark, since every hung part gets one somewhere.

Parts going down a powder or e-coat line need a hang hole or a hook point. If the part does not have an obvious one, say so early. Adding a process hole late in a project is a drawing change nobody wants.

Lot size, repeat rate and packaging

Give the parts per lot and, if it repeats, the expected annual volume or release schedule. A one-off run of 50 parts and a blanket order releasing 50 parts a month price differently even at the same lot size, because the shop can plan tank time and hold a slot for a repeat job.

Say how the parts should be packed after finishing. Bulk in a bin is fine for hardware; cosmetic or precision parts usually need individual packaging to avoid contact marks and scratches picked up after the coating is already on.

Tests and paperwork

List what has to come back with the lot, not what you assume is standard:

Thickness readings, with the method and how many parts or points get measured.
Adhesion testing, such as a bend or tape test, if your spec calls for it.
Salt spray per ASTM B117 on panels or parts, if corrosion life is being verified.
A bake record for hardened steel, with time and temperature.
A certificate of conformance naming the spec, type and class.

Paperwork you did not ask for is paperwork you will not get, and paperwork requested after the parts ship is often paperwork the shop cannot recreate.

A copy-ready RFQ template

Paste this into an email or attach it with the drawing:

Part name and number: Base material and condition: (alloy, temper, hardness if heat treated) Finish and spec: (finish, spec number, type/class, color if applicable) Thickness: (minimum or range, on which surfaces) Dimensions before/after finish: (yes/no, which features) Masking: (areas and requirement: bare, thin film, full finish) Handling: (barrel, rack or line; hang hole if any) Lot size and repeat rate: (one-off, or annual volume) Packaging: (bulk or individual) Tests and paperwork required: (thickness report, adhesion, salt spray, bake record, CoC) Quantity for this quote: Target lead time:

A shop can price from this in one pass. Attach the drawing and any model files, and note where the RFQ fields above are already called out on the drawing to avoid repeating them.

See also: ASTM B633 zinc plating specification: classes, types and callouts.

How we help

We are a matching service, not a plating shop. Send an RFQ with the fields above and we pass it to up to three finishing shops that run your process, hold your spec and have a tank, barrel or line that fits the part. They reply directly, usually within 24 business hours. If you are still deciding what to check before picking a shop, see how to choose a metal coating supplier, or go straight to the RFQ form.

Frequently asked questions

What is the single most common thing missing from a coating RFQ?

Whether dimensions apply before or after the finish. Threads, bores and press fits all change size with plating or anodize, and shops have to guess or ask if the drawing does not say which side of the finish the number belongs to.

Do I need to name a spec, or is a finish name enough?

A finish name alone leaves thickness, class and passivate open to the shop's default, which varies between shops. Naming a spec such as ASTM B633 or MIL-PRF-8625, even a commercial class, gets quotes that mean the same thing across shops.

How much detail does a prototype or one-off part need compared with production?

Less on paperwork, the same on the basics. A single prototype still needs base material, finish and spec, and where dimensions apply. Skip the test reports and bake records if the part is not going into service, but say so on the RFQ.

Can a shop quote from a 3D model alone, with no drawing?

Some can rough a price, but they still need the finish, spec, masking and dimensional notes somewhere. Either put them on the model as a note or attach a short spec sheet with the file.

Need a quote for this finish?

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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