Rough spots after powder coat???

[Presta24]

I sent a set of wheels to have powder coated. The wheels are cast aluminum. Got a call today saying they were done but there were a few "rough" spots from when the wheels were cast. I went to pick them up and wasn't happy with the finish. For the most part the wheels looked great. But on several spots on each wheel it looked bubbled, for lack of a better term. looked kinda like what rust looks like on a car before it breaks through the paint. When I talked to the guy on the phone he said that he tried to sand them down with a DA but the rough spots were too deep. He said it was from casting them in the mold. I run molds every day myself, so I assumed what he meant was there were some grooves where the parting lines were at in the mold(the line where the two halves of the mold close) When I looked at them it was obvious too me that the areas could have easily been sanded down. So I don't know if the problem was during powder coat or a bad prep job. Every one had already left for the day except two people who were helpful and assured me they would talk to the correct person about the problem. About 15 min later I got a call from the owner stating he would get it taken car of. Any ways, my question to any one who has powder coated wheels is, did you have any of the same problems? The guy made it seem like this was quite common with casted wheels. That those blemishes are there from the factory but when they dip and paint the rims it covers it up. I got a GREAT deal on the coating compared to other places I called so I am thinking it was a poor prep job. I will update when I have more info. No pics, i should have taken one with my phone to post with this but did not.

 

[Applejack]

Pic??

Cast aluminum really gasses out a lot. Out gassing it before coating helps and should be practiced but is not a cure all. Putting on another coat would also help cover those ugly spots.
Can't be too sure but it sounds like they are being a bit lazy with their prep work.

 

[Presta24]

ya, thats what i assumed, he said they were too deep to sand out, which, ok, i can believe. But when I got there and ran my hand across the bad spots and onto the smooth spots it was clear that they were not sanded very well, if at all. The bad spots were higher than the good spots. i mold car spoilers, and we also prep, and paint them in house so even though the wheels are aluminum and i run ABS, im not an idiot and know what bad prep work looks like. what is ourgassing, sounds like its pretty self explanatory, but can u be more specific? thanks

 

[LMT556]

Its an outgassing issue with the base metal. They can get a lower cure paint and cure the powder at a lower temperature, this can help out gassing. There are also some types of powder coating that are designed for outgassing applications such as cast type parts.

Outgassing is basically a porous type metal is heated, during cure the powder coating begins to gel (or set) in place, if the surface is no longer molten due to temperature (the longer the dwell time in the oven and the higher the oven temp) than outgassing occurs. Basically the gas bubbles up through the semi cured surface, if it happens with a product with a long gel time, the coating can reflow and hide the defects, if the coating is already past its gelled time than you will see what appears to be a small collection of craters and other surface defects which are the result of the bubbles passing through the film and damaging its appearance.

 

[Presta24]

Its an outgassing issue with the base metal. They can get a lower cure paint and cure the powder at a lower temperature, this can help out gassing. There are also some types of powder coating that are designed for outgassing applications such as cast type parts.

Outgassing is basically a porous type metal is heated, during cure the powder coating begins to gel (or set) in place, if the surface is no longer molten due to temperature (the longer the dwell time in the oven and the higher the oven temp) than outgassing occurs. Basically the gas bubbles up through the semi cured surface, if it happens with a product with a long gel time, the coating can reflow and hide the defects, if the coating is already past its gelled time than you will see what appears to be a small collection of craters and other surface defects which are the result of the bubbles passing through the film and damaging its appearance.

Thanks, I hope they get this figured out!

 

[Presta24]

bump

 

[Applejack]

I run a metal finishing shop (powder coating included) and without having seen the wheels in question, it would be my guess that they could just scuff out the bad spots and re-shoot them. What color did you have them done? Any primer coat?

 

[Presta24]

I run a metal finishing shop (powder coating included) and without having seen the wheels in question, it would be my guess that they could just scuff out the bad spots and re-shoot them. What color did you have them done? Any primer coat?

I am not sure if they used any primer or not. I had em done matte black. They called me back today and the guy was kind of a jerk, I could tell he was irritated about working on the wheels. Telling me how much he hates cast wheels and how "this happens every time with cast wheels" keeps telling me they are not billet aluminum and thats why the bad finish. Arent all wheels cast these days? Who the hell can afford billet wheels? I asked him about any kind of a sealer or a primer they could have used to cover up the blemishes, he said not that he knows of, he would have to check with his supplier. Seems to me he is not very experienced with powder coating wheels. Any ways he said they are ready, said he sanded them down and re shot them. Kinda like it was no big deal to touch em up. I was like, then why didnt u do it the first time instead of trying to send me home with crappy looking wheels. Does your shop have problems with cast wheels? All the replys I have gotten, every ones wheels have turned out fine. If they are not up to par when I go to pick em up friday I will get pics.

 

[Applejack]

It really sounds to me like these guys don't know what there are doing or they are very lazy. I've shot literally hundreds of wheels and most of them were cast.
There is the odd occasion where one will "gas out" and it's no big deal most of the time. You just scuff and re-shoot. Some powders can be a real pain in the neck to re-shoot, but NOT Matte Black.
Are these guys new to the biz?

 

[Presta24]

It really sounds to me like these guys don't know what there are doing or they are very lazy. I've shot literally hundreds of wheels and most of them were cast.
There is the odd occasion where one will "gas out" and it's no big deal most of the time. You just scuff and re-shoot. Some powders can be a real pain in the neck to re-shoot, but NOT Matte Black.
Are these guys new to the biz?

I don't believe so. Maybe with the coating of wheels, but they had a very nice show room for their hand rails and the owner took me into the offices so I could get online and show him the trail team wheels so he know what I wanted. The offices were very nice! So i think there rail business does very well, I think their powder coating guy is just lazy and used to shooting newly extruded aluminum with little to no prep work. We will see how they look when I pick em up Friday.