Chemours TiO2 Pigment, C4 Powder Coating, and Clear Coat: A Quality Inspector's 4-Step Checklist

Somewhere in your plant there's a spec sheet that says too little and a purchase order that assumes too much. That gap is where quality problems start.

I'm a quality and brand compliance manager at a coatings distributor. I review every coated sample before it reaches the customer—roughly 200+ unique items a year. In Q1 2024, I rejected 7% of first deliveries. Not because the parts were broken. Because the coating didn't match the spec we thought we'd agreed on.

This is the 4-step checklist I run through for color-critical industrial coatings. It covers powder coating, clear coat, and the pigment choices that make or break a finish.

A note before we start: if you came here searching “titanium dioxide for dogs”, this article will disappoint you. I'll address that in the last section.

Step 1: Translate vague labels like “C4 powder coating” into measurable specs

The phrase “C4 powder coating” shows up on drawings a lot. If that's all the PO says, it's not a spec. It's a wish.

C4 is a corrosivity category in ISO 12944-2. It describes a high-corrosion environment: industrial or coastal, where humidity and salts accelerate corrosion. It does not tell you which resin, which primer, which film thickness, or which cure window. A powder coating intended for C4 service only becomes meaningful when you pair it with a system name and test requirements. As of January 2025, this is the basis I use for C4 reviews.

In my approval workflow, every vague label gets translated before the purchase order goes out. For a C4 project, the spec sheet needs:

• A certified coating system from the powder supplier (for example, zinc-rich primer + polyester or polyurethane topcoat)
• Minimum dry film thickness (DFT) in microns
• Substrate prep standard (such as SSPC-SP10/NACE No. 2 near-white blast, or ISO 8501 Sa 2½)
• Color tolerance (Delta E target)
• Cure schedule, including peak metal temperature and dwell time
• Solvent rub test requirement (acetone rubs)

Before I issue a PO, I also confirm that the powder supplier has test data matching the environment. A color card isn't corrosion data.

The conventional wisdom is to tell the applicator “meet C4 requirements.” My experience with 200+ unique reviews says that's the start of the negotiation, not the end. The real failures happen when someone interprets a category as a product. That's the part that costs money.

Once, I said “approved C4 system” on the phone. The shop heard “any dark grey powder.” The first batch looked smooth and correctly colored. Then the acetone rub test faded the coating. The cure cycle had been shortened by 8 minutes. We rejected the batch and requalified the powder system. Now every contract contains a line like:

“ISO 12944-2 C4; approved system A-77; DFT per approved system; cure 200°C peak, 10 min dwell.”

Yes, it's more paperwork. It's also a lot cheaper than a redo.

Step 2: Verify the pigment. For white and light colors, pigment is the story.

For white and light pastel coatings, titanium dioxide does the heavy lifting. That's why “Chemours titanium dioxide pigment” appears in my specs more than any other raw material. The Chemours Ti-Pure line gives strong hiding power and, more importantly, a repeatable undertone. I don't accept “white pigment” or “generic TiO2” in color-critical approvals. I ask the formulator to state the pigment supplier and grade on the approval letter.

Actually, titanium dioxide pigment chemistry is more than “white powder.” For exterior coatings, you want a rutile-grade pigment, not anatase. Rutile absorbs UV and holds up better in a C4 environment. That's one reason the supplier name matters. In my experience, batch-to-batch consistency matters more than the initial color. A lab can match almost anything once; the hard part is repeating it at production scale.

I went back and forth between two pigment sources for weeks. One offered Chemours Ti-Pure; the other offered a 6% cost break. On paper, the savings looked good. My gut said the undertone could drift. Ultimately chose Chemours because a color mismatch on a 50,000-unit order would eat the savings several times over. On a less critical product, the other source would be fine. That's the thing—the right pigment depends on the application.

In the lab, I run every approved color against the standard under controlled light. We use the Pantone Matching System as a communication baseline. For brand-critical colors, the tolerance is Delta E < 2. Delta E between 2 and 4 is visible to a trained eye. Above 4 is a rejection. Reference: Pantone Color Matching System guidelines.

During Q1 2024, we received a batch of 8,000 plaques for an architectural order. The white was off—a yellowish undertone that made the grey topcoat look green. The vendor said it was “within industry standard.” It wasn't. The colorimeter showed Delta E of 3.8 against the approved standard. The culprit was inconsistent pigmentation. After they switched to Chemours titanium dioxide pigment at the specified loading, the same recipe measured 0.9. We still had to scrap the first batch. That's the part I remember.

Step 3: Measure the cure profile, not the oven set point.

Most coating failures I see aren't visible on day one. They show up as poor adhesion, soft film, or solvent sensitivity. The cause is often under-curing.

The spec says “cure at 200°C (392°F) for 10 minutes.” The operator reads the oven setting, not the part's metal temperature. A heavy rack of steel parts absorbs heat differently than thin panels. So every batch gets a data-logged thermocouple on the actual part.

I once approved a quote from a new powder shop because the price was lower. First batch looked good. The solvent rub test told a different story, though—the acetone softened the film. The shop had reduced the oven temperature by 10 degrees to “save energy.” They also contacted me two weeks later because the parts had begun to dull in salt spray. The hardness never developed properly. Failed. We redid 5,000 parts. Bad chemistry.

The lesson, learned the hard way: if a clear coat or powder coating is under-cured, acetone is a great detector and a terrible fixer. Which brings me to the last step.

Step 4: Use acetone as a test, not a cleaning method.

“Will acetone remove clear coat” is a search term that gets a lot of clicks. Let me answer it directly: yes, it can. Especially if the clear coat is under-cured, thin, or overloaded with solvent. Acetone dissolves the resin and softens the film. That's why it's used in solvent rub testing.

But in the field, acetone on a clear coat is dangerous. A wet rag left on the surface for 30 seconds can leave a permanent haze. A careless wipe can strip an edge. I've seen a technician try to remove overspray from a new clear coat with acetone and end up with a silver-dollar-size bare patch. Worse, acetone runs. It wicks along seams and under trim, so the damage is always bigger than the original spot.

If you are intentionally removing a clear coat, use a full-fledged stripper or mechanical abrasion. Mask the surrounding area. Don't rely on acetone to “melt it off” evenly. If you're a formulator or applicator, use acetone only on test panels and exactly as the standards specify. One more thing: acetone is not a production-line cleaner. It can leave residue and soft spots. Use a dedicated solvent if you need to clean a coated part.

When this checklist doesn't apply

What about “titanium dioxide for dogs”?

Let me be honest. If you're here because a search engine matched “titanium dioxide for dogs” to this page, this isn't the article you need. Titanium dioxide appears in some food and pet products as a colorant, but the regulatory path, particle size, and quality controls are completely different from the pigment-grade TiO2 we specify in coatings. I'm a coatings quality person, not a veterinarian. I will not advise on pet food. If you're worried about titanium dioxide in dog food, ask your vet or an animal nutritionist. That's not me dodging the question—it's the honest boundary of what I'm qualified to say.

This doesn't replace a full ISO 12944 test plan

This checklist is for people with control over a coating specification. It doesn't replace a full ISO 12944 test plan. C4 is a starting point. If you're specifying a coating for a C4 environment, you need corrosion testing and surface prep verification, not just a color chip and an acetone rub. I recommend this approach for powder coaters, paint formulators, and quality managers who can demand real data. If you're a homeowner trying to use acetone to fix a clear coat, take the caution, not the shortcut.

Also, if your coating spec is for a product that will live indoors and only needs to look good, many of these steps are overkill. Pick the depth of checking to fit the risk. The same standard that protects a coastal guardrail doesn't make sense on a decorative shelf.

Bottom line

To recap, in the order I do them:

1. Translate C4 and every vague label into a measurable system.
2. Verify the pigment. For white and light colors, Chemours titanium dioxide pigment is my benchmark.
3. Measure the cure profile on the part, not the oven.
4. Test the film with acetone—then clean up the acetone before it cleans your clear coat.

Actually, that last sentence is the one I'd hang on the wall. Acetone is a quality tool, not a cleanup convenience.

Now go look at your current PO. Does “C4 powder coating” mean a system, or a wish? If it's a wish, you've got your first step.