Application guide / Version 1.0
A bath concentration is not a purchase specification
Turn an operation, an assay basis and a named test method into a request a supplier can actually answer.
Name the operation before you name the chemical
40 CFR 433.10 defines the metal finishing category by six operations—electroplating, electroless plating, anodizing, coating (chromating, phosphating, and coloring), chemical etching and milling, and printed circuit board manufacture—and then reaches forty further process operations, cleaning, heat treating, salt bath descaling, solvent degreasing and painting among them, whenever one of the six is present.
The regulator organizes this work by operation. A purchase request should too. Record the operation, the bath it feeds and the specification that bath must satisfy. A request that says only “acid for the line” omits the fact that determines nearly everything downstream of it.
Write the concentration with its basis
A percentage is not a specification until it carries a basis. Record whether the assay is expressed by mass or by volume, the reference temperature, and the document and revision the value came from. Ask a supplier for those same items rather than accepting a headline number, and note whether the figure is typical, a guaranteed specification limit, or a measured lot result.
This matters more in a bath than in most places, because both the make-up calculation and the analytical control chart depend on it. Two products carrying the same nominal percentage can require different additions. A nominal grade or concentration does not establish interchangeability between products or between suppliers.
- Is the stated assay typical, a guaranteed limit, or a measured lot result?
- What is the basis and the reference temperature for that value?
- Which document and revision is it taken from?
Bind the number to a method
40 CFR 433.11 incorporates the analysis methods of 40 CFR part 136 by reference. The regulator does not accept a measurement without the procedure that produced it. Part 136 governs reporting under the discharge permit program; it does not govern acceptance of a delivered drum.
The discipline still transfers. When a team sets an incoming limit, name the method and its revision beside the limit and the units. Then name who interprets a result that falls outside, and what happens to the delivered material while that is resolved. An unassigned disposition is the gap that turns a measurement into an argument.
Requirement → evidence → decision boundary
An editorial checklist for your review—not a table of product specifications.
| Requirement | Evidence to request | What it does not establish |
|---|---|---|
| Operation and specification | Named operation, bath identifier and the governing specification revision | An industry listing is not an application approval. |
| Concentration basis | Assay, mass or volume basis, reference temperature and document revision | A shared nominal percentage does not establish interchangeability. |
| Analytical control | Method, revision, units and the person who dispositions an out-of-range result | An approved method is not an acceptance limit. |
Make the open questions useful
Record requirements, evidence gaps and approval owners in a downloadable purchasing brief.
Open the requirements worksheet →Revision record
1.0 · September 12, 2026 — Source-based editorial edition. No original testing or product qualification is claimed.
For finishers and their purchasing teams specifying bulk acids, bases and salts. This collection does not design a bath, set an operating concentration, qualify a process, or make a discharge, waste or exposure determination.
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