Unfixable Flaws and How to Avoid Them

True or false: there’s no need to package parts before sending them to the finishing shop, because any damage caused in transit will be invisible after blasting and coating?

False.

While most people understand that freshly-applied powder coating needs to be babied on the ride home, there’s a persistent misconception that no matter what happens to raw parts, blasting and coating will hide all manner of scratches, dents, and gouges.

This is not the case.

We see two main problems with incoming parts that were poorly packaged:

  1.       Scratches.
  2.       Rusting.

Scratches

While it is true that sanding, blasting, and powder coating will effectively hide minor scratches, anything deeper than 1/8” will come back to haunt you after the powder coating is applied. Either the untreated gouge will remain visible, or repeated attempts to sand it down will cause a dip in the metal’s surface. Rather than filling in the divots, powder coating will hug every curve; any odd topography on your part’s surface will remain highly visible after the powder has cured.

Liquid coating is a bit more forgiving: we can apply primer, patch the scratch with Bondo, sand everything down, apply paint, and there’s a decent chance the part might come out looking alright – but by the time we spend all day doing that, it’s often cheaper for the fabricator to remake the part.

Rusting

Imagine that a customer brings us a stack of metal sheets, shrink wrapped (but not water-tight), that has been sitting outside at the fabricator’s for three weeks. On the outside, it may look perfect: the shrink wrap held up well during shipping, the parts didn’t move too much, and there’s no reason to believe they’ll be scratched. If it rained at any point during their outdoor storage, however, it’s likely that water will have seeped in between the sheets. Unable to dry, it will have caused rust (on steel parts) or corrosion (on aluminum parts) that we may not even notice until it’s time to blast the parts.

Yes, blasting is very effective at removing rust. However, even if we get the substrate down to near-white metal, the parts of it that were rusted will have a slightly different texture than the parts of it that weren’t rusted. It might not be noticeable until after the powder coating is applied – if the powder coating has the right sheen and you’re standing in a certain light, every inconsistency in the substrate’s texture will be spotlighted.

In short, if you want to avoid re-making parts, it’s best to spend a little time thinking through your storage and packaging strategy before shipping them to us. Shrink wrap (or steel banding) is your best weapon against too much rattling. Cardboard or foam will keep parts from rubbing against one another. And if your parts have to wait a while before shipping to us, make sure they’re stored indoors, where they’ll stay dry. 

 

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