Metal finishing & surface treatment handbook

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.

Ask for the certificate, and say which one

Alliance sends a Certificate of Analysis when a customer asks, at no charge. Put the request in the purchase order, and say which document is meant. A sample or typical certificate describes what the product has looked like; a lot certificate reports results for the material being shipped to you. In a records file the two are not interchangeable.

Record what the certificate is expected to contain before it arrives: the analytes, the methods, the units, and the reporting limit for each. A certificate reports what was measured. It makes no statement about anything that was not on the list, and a species below a reporting limit is a limit, not a zero.

• Is the document a typical/sample certificate or a certificate for the shipped lot?
• Which analytes, methods, units and reporting limits does it actually cover?
• Which of your specification limits are not addressed by it at all?

A discharge standard is not a purity specification

40 CFR 433.15 sets pretreatment standards for existing sources in milligrams per liter, as a maximum for any one day and a monthly average: cadmium 0.69 and 0.26, chromium 2.77 and 1.71, copper 3.38 and 2.07, lead 0.69 and 0.43, nickel 3.98 and 2.38, silver 0.43 and 0.24, zinc 2.61 and 1.48, and total cyanide 1.20 and 0.65.

Those are limits on what leaves a plant, measured at a regulated point. They are not limits on what arrives in a drum, and borrowing them as an incoming-material specification is an easy substitution to make and an expensive one to unwind. Incoming limits come from the process specification and from bath control experience. Where the specification names no limit for a species, that gap is a question for the process owner, not a number to lift from an effluent table.

Make the measurement traceable, or say that it is not

NIST describes metrological traceability as a property of a measurement result: the result can be related to a reference through a documented unbroken chain of calibrations, each contributing to the measurement uncertainty. The elements it lists include a clearly defined property, a full description of the measurement system, a stated value with a documented uncertainty evaluation, and a complete specification of the reference at the time of comparison.

That is a usable checklist for reading someone else’s number and for defending your own. Where an element is missing, record it as missing. An undocumented result can still be informative; it should not be filed as though it were traceable.

Every certificate has a revision

NIST certifies and supplies over 1,200 reference materials, and tells users to confirm that the certificate in their possession is current. The same check applies to a supplier document: a certificate describes a state of knowledge on a date, and an old one can be quietly wrong about a current product.

Where an internal bath analysis feeds an acceptance decision, record which reference the analysis was calibrated against and when. A finisher’s own laboratory result is evidence in exactly the way a supplier’s is—as good as the method, the reference and the uncertainty behind it.

Requirement → evidence → decision boundary

An editorial checklist for your review—not a table of product specifications.

Which rule applies is a determination

EPA’s summary of the metal finishing guidelines lists the same six operations as the regulation and notes that certain electroplating work falls under the separate electroplating category instead: job shops that own not more than 50% of the material they finish, independent printed circuit board manufacturers discharging indirectly, and operations in place before July 15, 1983. The page was last updated March 17, 2026.

40 CFR 433.10(b) then hands whole facilities to other categories—coil coating at part 465, porcelain enameling at 466, iron and steel at 420, aluminum forming at 467, and seven more—while 433.10(c) excludes existing indirect-discharging job shops and independent board manufacturers, who sit under part 413. Which part governs a given facility is a written determination somebody owns. It is not something a chemical supplier can read off a product.

Two provisions worth reading before sourcing

433.15(c) states that no user introducing wastewater pollutants into a publicly owned treatment works shall augment the use of process wastewater as a partial or total substitute for adequate treatment. The same anti-dilution sentence appears in the BPT, BAT, new-source and new-source-pretreatment sections. Additional rinse water is not a compliance strategy, and a sourcing decision made on that assumption is unsafe.

The TTO figure in those tables is defined at 433.11(e) as the summation of all quantifiable values greater than 0.01 mg/L across a listed set of toxic organics. 433.12(a) offers a certification alternative in lieu of TTO monitoring, conditioned on a solvent management plan that specifies the toxic organics used and how they are disposed of instead of being dumped. A solvent purchase can therefore land inside a plan the facility has already signed—worth checking before the order, not after.

The waste code can turn on the process, not the chemical

40 CFR 261.31 lists F006 as wastewater treatment sludges from electroplating operations, but excludes six processes by name, among them sulfuric acid anodizing of aluminum, tin plating on carbon steel, and zinc plating on carbon steel on a segregated basis. Cyanide baths carry separate listings: F007 for spent cyanide plating bath solutions, F008 for plating bath residues from the bottom of baths where cyanides are used, and F009 for spent stripping and cleaning bath solutions from the same, each coded (R, T). F019 covers wastewater treatment sludges from the chemical conversion coating of aluminum, with its own exclusions.

Read that list as a reason to name the operation precisely in the purchasing record. Two lines using the same acid can generate differently listed wastes, and the difference is the process, not the drum. Alliance does not make a waste determination for anyone’s stream; that belongs to the generator and its environmental professional.

An exposure limit is an obligation, not a product property

29 CFR 1910.1026 sets a permissible exposure limit for chromium (VI) of 5 micrograms per cubic meter of air as an 8-hour time-weighted average. An action level of 2.5 µg/m³ as an 8-hour TWA triggers periodic monitoring at least every six months, and exposures above the PEL require it at least every three months. The standard excludes a process only where the employer holds objective data showing that it cannot release Cr(VI) at or above 0.5 µg/m³ as an 8-hour TWA under any expected conditions of use.

Those numbers describe air in a workplace, not a specification on a delivered drum, and no purchase document can supply the exposure assessment. What a purchasing record can carry is the name of the person who owns that assessment and whether any objective-data exclusion has actually been established and written down. Handling requirements stay with the exact product SDS and the site procedure.

• Which effluent guideline part governs this facility, and who determined that?
• Does an existing solvent management plan constrain what may be purchased?
• Which waste listings does the operation generate, and who signs that determination?
• Who owns exposure assessment, and is any objective-data exclusion documented?

Requirement → evidence → decision boundary

An editorial checklist for your review—not a table of product specifications.