Complete coverage?

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exceptional
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Complete coverage?

Post by exceptional »

Here is a pictures of my issue. This doesn't happen a lot, but enough to mess up a few projects. First, can this be fixed? Second, what causes it? It was a good, complete coat, exactly 20 min at 450. I do this every time and get very good results. Except once in a while, this happens. Oh, same powder coating used on each project.

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AnotherDano
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Re: Complete coverage?

Post by AnotherDano »

Overbaking? Most powders are 10minutes @400.
Are you using PMT? Part Metal Temperature?

It could be contaminants on the steel causing inconsistent coverage. The lighter areas on the piece look like they have a thinner coating than the rest.

Not enough info!
Is there a base coat? What powder are you shooting?
Is that hot rolled, P&O or cold rolled?
What color socks were you wearing? :lol:
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exceptional
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Re: Complete coverage?

Post by exceptional »

Not sure what PMT is? I buy my powder from Eastwood, that would be the standard they sell. This is hot rolled metal, acid treated for 24 hours, sanded and then powder coated. I tried heating the metal before coating but that didn't seem to be the best option. No base coat, would that help? Haven't heard of the base coat method yet. I will try the 10 min @ 400 and see how that works. Most all the videos I have watched said 20 min at 450 - 500. But I will try your suggestion. I am self taught as it may be obvious. I appreciate your suggestions and I will try it this week. I like 10 min better then 20 min anyway.
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AnotherDano
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Re: Complete coverage?

Post by AnotherDano »

exceptional wrote:Not sure what PMT is? I buy my powder from Eastwood, that would be the standard they sell. This is hot rolled metal, acid treated for 24 hours, sanded and then powder coated. I tried heating the metal before coating but that didn't seem to be the best option. No base coat, would that help? Haven't heard of the base coat method yet. I will try the 10 min @ 400 and see how that works. Most all the videos I have watched said 20 min at 450 - 500. But I will try your suggestion. I am self taught as it may be obvious. I appreciate your suggestions and I will try it this week. I like 10 min better then 20 min anyway.
PMT is Part Metal Temperature. You'd do well to get an electronic heat meter (thermometer). You can find them at any big box hardware store for about thirty bucks. Your timer should be set when the piece is at-temperature, not what the oven says it is. Most powders are somewhat overbake tolerant but 450~500 is in the burn-off range. Way too hot.

Heating the piece before shooting powder is called 'hot flocking'. If your powder melts on contact the piece is too hot and coverage will be very hard to control. Shooting 'warm' has its place but it takes a lot of experience and trial & error to get it right.

I asked about the base coat because the powder looked almost like a transparent or candy color in the photo.

At risk of offending our Admin or breaking forum rules, I will recommend powder365.com and its powder coating forum. Everything you'll need to get off on the right foot is there. You'll also find some familiar names there - right Largemouthlou? (Admin; If this is a no-no, please delete and forgive).

Eastwood is notorious for bad instructions on time & temp.

Hot rolled steel is my last choice for powder coating. The densities seem to have too much variance in its properties. It's like that cake your little sister made with pockets of flour in it. :o

And, as much sanding, grinding and polishing that HR requires, cold rolled actually comes out cheaper. P&O is hot rolled that has been 'pickled and oiled'. That is supposed to remove all the mill scale but depending on the source, it can still have some scale present.
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Re: Complete coverage?

Post by Largemouthlou »

That be right on Dano!!!!!!!!!! :D
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plain ol Bill
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Re: Complete coverage?

Post by plain ol Bill »

Another tip - get an LED light (flashlight or drop light) and use it to check your part for full powder coverage before you put it in the oven. The LED light will show up areas not covered like a beacon in the night. Looks like you just did not get full powder coverage to me. 450 is too hot and then to compound it you are cooking too long. Wipe your part with denatured alcohol before coating to make sure any oils or finger prints are gone.
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exceptional
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Re: Complete coverage?

Post by exceptional »

A lot of great information and I can improve my process with this new information. Thanks for taking the time to help me.
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Re: Complete coverage?

Post by wghughes7 »

I usually bake my parts at 400 for 20 minutes for regular powders. For high temp powders I bake at 450 for 20 minutes. Since the piece you coated is not very thick, try baking it at 400 for 20 minutes, also you may not be getting a good ground. When I do not have a good ground the powder will not stick everywhere and leave spots. Try the powder from Prismatic Powders. I have only had one problem with a powder from there and it was Splatter Copper. Any other color I have used has worked great.
exceptional
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Re: Complete coverage?

Post by exceptional »

Thanks for the info. I'l keep practicing till I get it right.
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