Coating Approval Checklist: 7 Quality Checks Before You Buy

I'm the person who reviews coating specifications before they're approved for shipment. In 2024, I rejected about 12% of first submissions—not because the products were bad, but because the spec didn't match the customer's actual application. Whether you're buying powder coatings, a coating for flat roofs, or a drum of acetone, the same discipline applies. The checklist below is what I run through on every order. If you're on the specifying or purchasing side, it'll help you find the gaps before they become field failures.

There are seven checks, in the order I run them. Some look obvious at first glance. Check #5 is the one most buyers skip, and it's the one that causes the most expensive surprises.

Check 1 — Match the Spec Sheet to the Real Application

Spec sheets are written for ideal conditions: clean substrate, controlled temperature, proper surface prep. Real job sites aren't ideal. When I compared two projects side by side—same coating, same batch, different surface prep—I finally understood why details matter so much. The panels looked identical in the lab. On site, one delaminated within eight months.

Before you approve anything, verify three things:

• Substrate type and condition (bare metal, galvanized, aged concrete, existing coating?)
• Exposure class (UV, chemical exposure, ponding water?)
• Surface prep requirement (blast profile, etch, primer?)

Check 2 — Verify the Solvent System, Not Just the Color

A lot of buyers focus on viscosity and color. They only dig into the solvent package when something smells wrong—literally. That's backwards, because the solvent system controls how the coating flows, levels, and cures.

Take acetone products, for example. The question everyone asks is 'is it pure acetone?' The question they should ask is 'what's the water content and distillation range?' Acetone is hygroscopic; it pulls moisture from the air. A drum that's been sitting half-open can hold enough water to cause fisheyes or blushing in your finish. I've seen it happen (and, predictably, the applicator blamed the coating rather than the solvent).

Here's a chemistry detail that matters more than you'd think. How many hydrogen bonds can methanol form? Two per molecule—one as a donor through the hydroxyl hydrogen, and one as an acceptor through the oxygen lone pairs. Acetone, by contrast, can only accept hydrogen bonds. That difference changes evaporation rates, which changes how a coating dries and levels. When someone substitutes a solvent on the fly, you're not just changing the smell. You're changing the film formation. Check the solvent spec before approving any substitution.

Check 3 — Coating for Flat Roofs? Verify the Ponding Rating

This one catches a lot of good buyers. A 'flat' roof is rarely flat—there's almost always ponding after heavy rain. Most coating data sheets rate for flow and drainage. Ponding water resistance is a separate spec, and it's easy to miss.

I recommend a roof coating with verified ponding resistance when your roof has no slope to drains, old insulation creating low spots, or a documented history of standing water. If your roof drains well, a standard elastomeric coating is usually fine. If it doesn't drain well, no coating will save you—fix the drainage first. That's the honest answer. Roughly 80% of flat-roof projects can use a standard system; the other 20% need a ponding-rated membrane or a roof repair before coating.

Check 4 — Confirm Cure Time for Your Conditions

The failed launch in 2022 changed how I think about cure specifications. We approved a coating that met our application temperature requirements. It cured slower than our production line could accommodate. Parts were boxed while still tacky, and a customer opened a crate full of ruined components. That quality issue cost us a $22,000 redo and delayed our launch by three weeks.

The cure data on a spec sheet is measured on a lab panel at ideal film thickness. Your applied film thickness, your substrate's thermal mass, and your shop's humidity all change the real cure time. If you're running a fast production line, pay attention to the lower boundary of the cure window—not the midpoint.

Check 5 — Powder Coatings: Ask for Particle Size Data

Here's the one most buyers skip. For powder coatings, everyone checks color, gloss, and the cure schedule. Few buyers ask for the particle size distribution. That's a mistake, because particle size affects transfer efficiency, film thickness, and how much powder you reclaim.

If the distribution is too wide, you'll get thin spots and thick spots in the same run. If it's too fine, the powder won't fluidize properly and you'll see inconsistent feeding.

A trend I've been following in PPG powder coatings news is the shift toward low-cure powders that cut energy consumption. That's a genuine step forward. But even low-cure powders need particle size verification on your actual line. A powder that's been shipped and stored can have a different distribution than the lab sample from the brochure.

Check 6 — Log Batch Numbers, Keep a Retention Sample

When I implemented our verification protocol in 2022, we started logging batch numbers on every order and pulling a retention sample. It felt like bureaucracy at the time. It's saved us three times since.

Here's something vendors won't tell you: coatings are manufactured in batches, not continuous runs. Every batch has its own certificate of analysis, and every batch has subtle variation. If a failure shows up in the field, the batch number and retention sample tell you whether it's a manufacturing issue or an application issue. Without them, you're guessing—and guessing is expensive.

Check 7 — Always Run a Test Panel on the Real Substrate

This is the step almost everyone skips when a deadline is breathing down their neck. I get it—a test panel adds time and costs a few hundred dollars. But every coating failure I've traced to 'we saved time by skipping the test' has cost more than the test would have.

Run two panels. Prepare the first exactly per the spec sheet. Prepare the second using your actual substrate and your actual prep process. The difference between the two tells you more than any data sheet. On a recent job, the spec-sheet panel looked great while the real-world panel showed adhesion issues from silicone contamination we hadn't accounted for. Fixing the prep cost us nothing before the install. Skipping the test would have cost us the entire job.

Common Mistakes That Keep Showing Up

After four years of reviewing orders, I keep seeing the same three:

Assuming all acetone products are the same grade. They're not. Check water content, distillation range, and residue. An 'industrial-grade' label doesn't mean it's right for your application.

Ignoring humidity and dew point for roof coatings. Apply over a wet substrate or above the dew point and you'll get blistering. That's an application failure, but someone still pays for it.

Buying on unit price alone. Total cost includes solvent quality, surface prep, cure time, and the recoating cycle. A cheaper coating that cures slower or fails a year earlier isn't cheaper.

Why Verification Wins

You've seen the PPG Paints Arena schedule: 150-plus event nights a year, from hockey games to sold-out concerts. The coatings in that building handle constant foot traffic, spilled drinks, and aggressive cleaning chemicals. That performance isn't luck. It comes from the same discipline—verified specs, checked batches, and honest test panels.

I've been doing this long enough to know that no checklist catches everything. When I say 'long enough,' I do not mean a couple of years—I mean reviewing 200+ orders a year for over four years. But a checklist doesn't need to catch everything. It needs to catch the failures that are common and expensive. Seven checks, twenty minutes, and you'll be far more confident in the coating you're about to approve.