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Anyone here good at DIY powdercoating? I figured while I'm doing my engine swap I'll start powdercoating the various suspension components and brackets that are starting to get a coating of surface rust so I picked up a powder coating kit. We'll I've made two attempts to powdercoat small scrap test pieces before starting on the real parts and so far I have not gotten a good even coat. Both times I sandblasted the metal first. The first attempt was due to being out in the driveway and the wind blew most of the powder everywhere but the part. Lesson learned, next attempt was in the garage with the doors closed. This time it appeared to work fine, looked like a good even coat of powder on the part but after baking the middle was really thin and you could see the metal through the coating. How do you know you've put enough powder on the part? Could it be oven temperature? I need to get an oven thermometer to verify the temp. Any tips/tricks more experience people can share would be appreciated.

I did quite a bit a few years ago using an old electric oven.

After you've done a few parts you usually develop an eye for what the powder should look like when its evenly applied. If I couldn't see the metal through the unbaked powdered I knew I was good. Typically the electric charge is only strong enough to hold the right amount of powder and anything extra falls away.

Did you clean it with acetone before applying the powder?

I don't know how much it matters but I've also preheated the part for ~20 minutes before applying the powder. The powder melts immediately and sticks so you don't have to worry about knocking it off.

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I've never done powder coating, but from my experience,

I would recommend a phosphate treatment before any powder coating.

It is a common industrial pretreatment for painting steel and is used for powder coating too (from what I read on the internet, so it must be true)

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Chuck.

“Any suspension will work if you don’t let it.” - Colin Chapman

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Prior to retirement, my job was to inspect industrial discharges to the sanitary sewer. I soon discovered that any serious industrial painting or coating facility employed a phosphate treatment. It is a simple and very effective step in the process. It acts as a final cleaning step, removes any minor rust that may be present and etches the steel, giving the finish something to "hang onto".

So yes, it is true.

Bill

I'll have to try acetone, I was hoping I was okay cleanliness-wise going straight from sandblasting to powdercoating but maybe I'm leaving some residue. I've read about pre-heating but I thought that may get cumbersome with some of the larger pieces but I'll have to experiment with it.

I'm not familiar with the phosphate treatments? Any specific products people have experience with?

I just did a few pieces and I did a thorough sand blast and then coated.

BUT BEFORE I BAKED IT, I used a bright LED flashlight to check for thin spots. I found a few, re-hit it with the powder and everything came out fine.

How do you do the phosphate coating?

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mobilito ergo sum
I drive therefore I am

I can explain it to you,
but I can't understand it for you.

Thanks for the help. Re-sandblasted the piece, cleaned it with acetone, pre-heated it and then coated it longer. Seems to have worked out better this time.

May be too late, but.....

Phosphoric acid, applied at room temp with a scotch-brite pad is used in our hobby to remove rust. Do not confuse it with muriatic acid (aka hydrochloric acid) which is much different. In addition, it will form with good iron (steel) to form iron phosphate. This is a stable compound which is a great base for painting. In and of itself, it is a rust preventer for short periods. It also helps to form a great bond between the base metal and paint (or powder coating). The company I used to work for, had a sheet metal dept. We punched sheet metal and painted it. Phosphae wash wwas used to prep the steel, i.e. degrease and derust.

It is also used in water softeners to remove the iron fouling of the pellets in the softener (not the salt pellets).

Phosphoric acid can be found in paint departments, chemical sellers, and many other places. It is sold under many trade names. Ospho is but one.

_________________
Chuck.

“Any suspension will work if you don’t let it.” - Colin Chapman

Visit my ongoing MGB Rustoration log: over HERE

Or my Wankel powered Locost log : over HERE

And don't forget my Cushman Truckster resto Locostusa.com/forums/viewtopic.php?f=36&t=17766

I can add only that while I can understand the use of the Scotch-Brite pad to help remove rust, it is not necessary and I never saw a commercial setup that used abrasion to aid the phosphoric acid.

Bill

Right you are Bill. The system I have seen was pressurized and heated on relatively new sheet steel, we went to electrogalvanized steel. I think we still used the phosphate wash to remove the oils.

I did say that the scotchbrite was for hobbyists. I see it may have been misread as also being used in a production environment. Wasn't my intent.

I always had a container of phosphoric acid anytime I was actively building my car. I'd drop nuts and bolts into it and hours to a day later, I'd pull them out and take a wire wheel to them. It did a great job of derusting. And they shined like new except for the pits. The wire brush took any protective coating off and I was left with bare steel bolts, Shiny, but started rusting quickly. I could (should) have phosphatized them after removing the "gunk".

_________________
Chuck.

“Any suspension will work if you don’t let it.” - Colin Chapman

Visit my ongoing MGB Rustoration log: over HERE

Or my Wankel powered Locost log : over HERE

And don't forget my Cushman Truckster resto Locostusa.com/forums/viewtopic.php?f=36&t=17766

Thanks, Chuck.
That's good info. Does the phosphoric acid need to be washed off before priming/painting? Or is the intent to have it interact with the steel and form a layer for the primer/paint to bite into?
I have used an acid etch to paint aluminum panels, but that required good washing before painting.

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Martin


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