Anyone who has spilled spaghetti sauce on a white button down, cleaned fingerprints off of a white wall, or tried to keep a white car dust-free knows: the color white tends to be higher-maintenance than most.
This is true in the liquid and powder coating world as well, with an added variable: rust. I cringe a little any time a customer requests white powder coating on outdoor railing, so I wanted to take a moment to voice my concerns about the color white.
Let’s imagine a railing was blasted and powder coated white. Let’s also imagine, for the sake of argument, that this job was done well – the blasting and coating shop in question did everything right, blasted to near-white metal, pretreated the part effectively, applied a solid coating with no visible surface issues, and took all necessary shipping precautions.
Now let’s imagine there’s a single pin hold around the weld that the powder didn’t completely seal, or perhaps a crevice between two parts of overlapping metal that the powder coating can’t penetrate. And imagine that the part gets rained on. What happens then? Water gets into the pinhole or the crevice. It comes in contact with the metal, and takes on an orange hue. When it runs back out of the pinhole or crevice, it’s going to deposit that orange stain on the part’s surface, creating what I call “rust streaking.”
Rust streaking does not necessarily indicate deeper rust issues, or even serious surface coating issues; it’s no cause for alarm, and may even be easily wiped off. But it’s unsightly and annoying, and it stands out dramatically against white parts.
Anyone who knows us knows that we always blast outdoor parts before powder coating them – that’s standard operating procedure at Kaser, because it’s the most effective way to ensure the coating’s longevity, in any color. If we know we’re powder coating in white, however, we’ll take some added precautions. For instance, we’ll strongly recommend that the customer let us blast the part to near-white metal ourselves, rather than bringing us a part that’s been commercial-blasted elsewhere. Near-white metal is a cleaner, smoother, less oily substrate, and the cleaner the substrate, the better the odds of avoiding rust streaking. We want to know that the job is done right.
Additionally, we’ll modify our pretreatment and powder coating process to help avoid rust streaking on white. We’ve come up with a great combination over the past several years. It’s not fool proof, but every bit helps.
If the part has overlapping metal pieces that can’t be coated, we’ll strongly recommend a seam seal, which cures in the oven and helps keep water out of crevices.
But most importantly, I’ll make sure to talk to the customer. It’s important to me that they know the risks, and if white proves to be too high maintenance for them, we’ll look into off-white or gray instead.
Readers, take heed: approach white coatings the way you would a white bedspread, and ask yourselves if it’s worth the trouble to keep it clean.