The first car I ceramic coated was my 2019 Focus RS. I washed it, dried it, applied the coating, and felt pretty good about myself. Three months later, the water behavior had degraded significantly. Six months in, it was basically gone.
I blamed the product at first. Tried a different brand. Same result. Then I started actually listening to what the detailers in the forums were saying, and it hit me—I had skipped a crucial step.
I never decontaminated the paint.
Paint decontamination is the process where you remove bonded contaminants from the surface. Iron particles from brake dust, industrial fallout, tree sap, all the gunk that works its way into your clear coat over months and years. A wash gets the loose dirt. Decontamination gets the stuff that sticks at a molecular level.
Here's the thing about ceramic coatings: they bond to whatever's on the surface. If you trap contamination underneath that bond, your coating is basically gluing itself to a dirty foundation. It's like painting over peeling wallpaper—the paint goes on fine, it just doesn't stay there.
Two Types of Contamination
Ferrous contamination comes from brakes and industrial sources. Organic stuff is sap, bugs, pollen. Then there's just general bonded dirt that accumulates over time.
A clay bar handles most of it. An iron remover specifically dissolves the ferrous particles. Used together, they leave you with a genuinely clean surface—not just one that looks clean.
The process looks like this:
I know it sounds like extra work. It is. But it's the difference between a coating that lasts two years versus one that looks decent for six months.
The Moment It Clicked
I redid my RS last spring—this time with full decontamination first. Iron remover, clayed every panel, then applied the same ceramic coating.
Eighteen months later, the coating is still going strong. Beading is excellent. Water still sheets off like it should. The difference wasn't the product. It was the prep.
I got cocky the first time. Washed the car and figured that was good enough. It wasn't.
What This Means For You
If you're planning to apply any protection—ceramic coating, SiO2 sealant, even wax—do yourself a favor and decontaminate first. It's not glamorous work. You won't notice a difference right away. But it creates the foundation for everything that comes after.
Iron remover costs about $15-20. A clay mitt runs around $25. That's $40 and maybe 45 minutes of work to dramatically improve your results.
The Kernastra Company is building tools to help you track your car's maintenance history—because remembering what you did 18 months ago is harder than it sounds. For now, if you're getting ready to coat your car and you skipped the decontamination step, you're probably going to regret it.
Early access is open at thevaultbay.com if you want to follow along.