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View Full Version : Powder Coat:: Is it & Prep



Paul Alciatore
03-20-2019, 04:36 PM
I have some scrap steel with a black finish.How can I tell if it is powder coat or paint?

And if paint, do I have to completely remove it before applying powder coat?

dalee100
03-20-2019, 04:40 PM
Hi,

Isn't powder coat pretty thick?

If you want to powder coat metal, it needs to be clean and shiny for best results. So paint removal is a must.

paul463
03-20-2019, 06:27 PM
Try sanding it off. My experience with PC is that it sucks to try sanding off.

I much prefer paint over powder coating.

CCWKen
03-20-2019, 06:46 PM
Put a little paint stripper in an inconspicuous spot. If the coating just laughs at you, it's PC. I had to buy some industrial strength PC remover. It's so strong, it will strip anodizing off aluminum as well as PC in seconds.

3 Phase Lightbulb
03-20-2019, 07:02 PM
I've done a lot of powder coating in the past and I've always sandblasted in prep for powder coating. I powder coated all of the suspension components on my buggy. I even got a powder coating oven. I have not powder coated anything in over 12 years and I wonder if all of my powders are still good. I might need a new powder gun too.

http://www.bbssystem.com/pictures/pc1.jpg

http://www.bbssystem.com/pictures/pc2.jpg

http://www.bbssystem.com/pictures/pc3.jpg

http://www.bbssystem.com/pictures/pc4.jpg

http://www.bbssystem.com/pictures/pc5.jpg

Yondering
03-20-2019, 07:15 PM
If you can heat a piece of scrap with a torch - paint will burn off pretty easily, as I'm sure you know. Powder coating is more resistant to heat, going to a much higher temp before it turns black and then finally to ash.

I powder coat my cast lead bullets, and of course the rejects just go back in the melting pot. It's interesting to watch the lead melt out of them (at around 650-675 F) leaving the skin of powder coating intact and floating on the lead. That skin generally chars black at around 750 F.

Edit - to be fair, there are a couple different types of powder coating. The type I'm describing is TGIC polyester.

ed_h
03-20-2019, 08:16 PM
1. I'm not sure that most ordinary paint will take the heat needed for PC curing, typically 375-450 F for at least 20 minutes.

2. Ordinary Methylene Chloride paint stripper will remove typical PC.

3. PC is normally thicker than a coat of typical paint, but multiple coats of paint could be as thick or thicker than PC.

Ed

Paul Alciatore
03-20-2019, 11:28 PM
I will try sanding it first just to see how that works, but this looks like a winner. Wish I had thought of it. Thanks!

So, no paint under the powder coat, but powder coat under paint is OK?




Put a little paint stripper in an inconspicuous spot. If the coating just laughs at you, it's PC. I had to buy some industrial strength PC remover. It's so strong, it will strip anodizing off aluminum as well as PC in seconds.

Noitoen
03-21-2019, 02:57 AM
Don't they PC over PC as well. I've seen, especially on wheel rims, powder coat a base colour and then PC a clear coat.

ed_h
03-21-2019, 09:41 AM
I've done PC over PC, but usually just flow the first coat without fully curing it. After applying second coat, a normal oven cycle cures both coats.

Ed

Bob La Londe
03-21-2019, 11:08 AM
Don't they PC over PC as well. I've seen, especially on wheel rims, powder coat a base colour and then PC a clear coat.

We use powder coat in some types of fishing tackle. One trick is a brush flick method for laminated colors. Usually I am just using a heat gun and a fluid bed. then while the base coat is still warm I'll use a flux brush to pick up another color and tap or flick the brush to get a bit of another color on one side. Usually the top. If it doesn't sick a quick pass back in front of the heat gun to warm it up will do the trick. Then into the oven.

For the fellow wondering about his old powder coat. Moisture is the killer. I always seal my powder coat jars immediately after working, and the bigger jars get a decent size packet of silica gel in the top. Otherwise there is no reason it shouldn't last indefinitely. If you open the jar and pour some out you can tell. If it flows almost like water with no tiny clumps its probably fine. I use Pro-Tec and Harbor Freight powder coat.


For anybody.
Powder coat isn't all that big a deal for small parts. I can't speak for larger parts. I have a static gun, but its not powerful enough for anything I ever really wanted to use it on. For small stuff I just use a heat gun or a torch to warm the part. I can get a thinner more uniform coating with a fluid bed, but sometimes I just dump some powder out in a small dish and swirl the warm part around in it. If its just for show you can get away with just warming it again in front of the heat gun until the plastic goes glossy and flow smooth, but its not very strong. For a strong coating I always bake in a little toaster oven that sits on top of the microwave I use for cooking plastisol. Some guys claim two heats is better, but I found one heat per the instruction on the bottle works just fine. Then I just crack the oven door and let the parts air cool normally. Of course when I say small parts. I can often hold them in the palm of my hand. Sometimes several. Typically people only powder coat metal parts, but in my reading I have run across references to powder coating other materials. Obviously you can't use a static gun on a wood block, but my heat gun method should work as long as it can take the heat. I've never spoken with anybody who has done anything other than metal parts. I might experiment someday if I ever have any spare time.