I guess I'm doing something wrong....

[black94t]

So, I had this red powder from HF and I powder coated a valve cover with it. Dry adhesion was great. I put it in the oven and after flow out, some places looked like someone fired a shot gun at it (pellet spread). Looks like a cluster of pores, in other words. I thought it might have been the powder because I spend a lot of time prepping the covers and the cover sits in the oven for at least an hour to outgas (at 400).

So then I used EW mirror black and it smoothed out real nice, but then again, I got those custer of pores. So, I let the cover completely cool and put a cooled layer of powder over the entire cover again and it gets a bit wavy (more than likely due to heavy powder thickness).

Surely this is something quite common and is already remedied. This has to be something I'm doing or not doing.

Can I hear some experiences and change in technique that eliminates this?

Thanks.

[Harleydad]

What do you do after outgassing as far as prep.
I outgas at a temp 50 degrees higher than I'm going to cure the powder at.

[black94t]

yeah I think I read what you just said about 50 times before posting my issue

Outgassing is the very last prep step I take before powder coating. I know there's a debate on blasting and outgassing but I tend to believe outgassing should be the final step. Of course, it is always a possibility I'm wrong

Should I be doing something different? Basically it's like this: clean/degrease, heat to 150 degrees, then blast (I find blasting works a bit better when the substrate is at an elevated temp), then outgass, then coat. Let me know what you think about that. Feel free to flame me. hahahaha. Thanks!

[Harleydad]

You need to either clean/degrease or blast after outgassing also. All that **** you're trying to bake out is sitting on the surface.

[black94t]

Well, I do rinse after blasting. I rinse with hot water and/or I'll wipe it down with acetone. I read somewhere that acetone softens aluminum, not sure how that affects the coating, but some are saying to use denatured alcohol. I picked some of that stuff up tonight. We'll see how that works.

[Harleydad]

Originally Posted by black94t

Well, I do rinse after blasting. I rinse with hot water and/or I'll wipe it down with acetone. I read somewhere that acetone softens aluminum, not sure how that affects the coating, but some are saying to use denatured alcohol. I picked some of that stuff up tonight. We'll see how that works.

Acetone will not soften aluminum. It will soften powder. If you sand a 1st coat to apply a second (for whatever reason) don't use acetone to wipe down. Thats where the denatured alky comes in. Try this:
1. clean/degrease (rinse well)
2. Blow dry with clean air
3. blast
4. Out gas 50 degrees above cure temp for an hour
5. clean/degrease again (rinse well) or blast again (this is where the debate lies on which is better to do after outgassing).
6 Blow off with clean dry air
7. Coat and cure.
As a side note: I don't wipe down blasted surfaces with lint free rags and acetone or denatured alky anymore. After blasting it's just a back type shower brush and clean dry air. If you feel you need to wipe them down it helps to go over the part with hand held propane torch to remove any rag lint.

[black94t]

If I do put 2 coats down, is it mandatory I sand it down? I'm assuming sanding it will put some texture on the powder to give adhesion to the powder? I never thought of that (though this is not related to my thread topic).

I will definitely try the way you described. It's real close to what I'm doing, but this may be a matter of tweaking the process a little to get it right. I also just switched to aluminum oxide 70g to blast parts and I just did some wheel centers and I have to remark that they look better than glass beads. And in less time. I think there is a combination of things, but I'm going to focus on ensuring no water or vapors are in my air lines and to ensure there are no foreign particles on the substrate.

As always, thanks for your input. I get excited when I see "harley dad" posting replies

[JTW37]

I ain't HD, although he's a pretty cool dude, but I found the same thing with the HF red. It pinholes for whatever reason. Probably comes from China and all their $hit is just that. Well except for the flat black. It seems to work good for a base or whatever. But the red, I think is just pure cheap ****.

Also, if you follow HD's method, you shouldn't have any issue's. It's a good workable method.

[Harleydad]

Originally Posted by black94t

If I do put 2 coats down, is it mandatory I sand it down? I'm assuming sanding it will put some texture on the powder to give adhesion to the powder? I never thought of that (though this is not related to my thread topic).

I will definitely try the way you described. It's real close to what I'm doing, but this may be a matter of tweaking the process a little to get it right. I also just switched to aluminum oxide 70g to blast parts and I just did some wheel centers and I have to remark that they look better than glass beads. And in less time. I think there is a combination of things, but I'm going to focus on ensuring no water or vapors are in my air lines and to ensure there are no foreign particles on the substrate.

As always, thanks for your input. I get excited when I see "harley dad" posting replies

Thanks for the kind words guy's.
JTW could be correct that it may be the powder, although you stated you had the same trouble with EW Mirror black.
As far as sanding for a second coat, you are correct, aid in adhesion is why it's done. Now, there are certain scenarios when to sand and when not to. Thats a whole other topic.
The theory is glass beads will embed themselves in the aluminum, switching to AO should help.
I've been following the Eastwod post also. Some good tips there as well. This thread is specifically about the aluminum valve covers. I should have asked, do you have these problems with everything or just this particular job? Contaminated air could also be the culprit. Take your air line and shoot it at a clean white piece of paper for a couple minutes, see if anything shows up.

[black94t]

Well, I did a 56 ford shift sleeve and had the same issues with the EW mirror black. I did a water inlet with the HF red and it turned out real good.


This is my first valve cover (very first valve cover....ever lol)


You can see the wavy texture and that is from the 2nd layer of powder (to fill some of those pin holes or pores, as I call them).

Can I just get any air separator, say, from Oreilly's? I could get it today and get some powder coating done today (without waiting)....

I also sprayed the air on a white sheet of paper and I get nothing coming out. I don't see any faint water lines. I hold it up in the light to see if I can see anything and it's just as clean as when I started.