powder coating and sandblaster question

[fastcars]

I've been powder coating for the past 3 days. I’ve been using the gun from harbor freight and the powder from eastwood. I've been using the chrome color. My first time doing this was 3 day ago too. The problem I'm having is that I keep getting orange peel. The first piece I did had so much that I had to wet sand it to smooth it back out and redo it. It still looked bad so I sandblasted it to bare metal again then did it over. It came out better but still had orange peel on it. I put the clear powder coat over it to see if that made it look any better, but it just made it look pitted. I don’t know why it was pitted since I never touched it, it wasn’t dirty, i just pulled it out of the oven and powdered it. I followed all the direction and temperatures. The clear calls for 340 degrees and the chrome color is 375. Does anyone have experience with that that can help me get a nice smooth finish like you would when painting a car?

My sandblaster: I have to types of sandblasters. I forget what they are called but one is a cabinet blaster. That one doesn’t have anything attached like a vacuum or anything. My other one is like a smaller sized air compressor. You fill with sand, attach the compressor hose, put your protective clothing and hood on and spray sand all over the place. That particular one is awesome and takes the rust and paint off real fast. But its messy and you gotta stop every time it empties out. My cabinet sandblaster is ok but it takes sooooo long to sandblast anything. What can I do to make my cabinet sandblaster much stronger so I don’t have to take about 45 minutes to do an A-arm? What do you guys use? If it matters, my compressor is 7 1/2 hp and its not a Craftsman, so It will handle sandblasting.

 

[3483x2]

Based on your process description, I didn't read anything about allowing for initial flow.

Once the powder is applied, you need to heat the product to about 250 degrees allowing for a smooth textured flow.

Once complete, raise your heat to the suggested temp and time.
i.e. 350 for 20 min.

If I read your symptoms correctly, you should get the results your after with this step.

Hope it helps

 

[3483x2]

To your second question, I would ask what type of media is in your cabinet?
Sand, Bi-carb of soda, walnut shells etc. Different media have various strengths and limitations. If everthing else is equal, I would then check for blockage in your cabinet gun and hose.

If your portable unit is working for you but are dealing with the usual "sand is everywhere" give something like this some thought.

http://cgi.ebay.com/Texsport-PORTAB...66:2|39:1|72:1205|240:1318|301:1|293:1|294:50

My plan is to use something like this for my larger items which I can't fit in my cabinet. Hood, Trunk Lid, doors

Fashioning a "lipped" retainment base, (think refrig box end), I figure will improve my recycling of media and clean up. Out of use storage is minimal as well.

Once again, hope it helps

 

[w ogden]

Well, I have been blasting and powder coating for several years now and can say that I have never seen this. I use Eastwood products but have never used the chrome. I blast and preheat, then cool and then coat and into the oven at 400 for about twenty minutes. Never had any flow issues or orange peeling. May be that I have been lucky.
I blast with a 3hp ingersol 100 gallon tank. I use glass bead almost always and real fine. Never have any big issues here. I do change the media each time that I replace the blast screen on the site glass. And I have real dry air. Very important. A little moisture will screw up the works quickly. I drain the tank frequently and the water traps in the line. I blast at 70psi with the fine media and it seems to work out pretty well.

 

[60Impala4Dad]

blasting

I can't help you with the powder coat issue other than reminding you that Eastwood has a tech line for things like this.

As for the low output from your blasting cabinet compared to your other setup, if you are using the same blasting media and your pressure is the same, make sure that the orifice size is as small as you can get it in the basting gun tip. They tend to wear out and open up to a larger diameter, even more so with the ceramic tips. A larger blasting tip will allow more media to flow but at a lower speed, which would be consistent with what you are saying about it taking so long to blast a piece of material.
Also, since you are using a blasting cabinet it is possible that the media that you are using (glass bead, sand, ....) is worn out after too many recovery cycles and it needs to be replaced. Both glass bead and sand can turn to powder after so many cycles through the gun.

Good luck.
Doc

 

[fastcars]

I use sand when I sandblast. I use the same preassure all the time. The nozzled might be a little worn but when I first bought this cabinet, I had the same issue.... It took way to long to sandblast. Im going to go to Home Depot today and I'll buy some more sand and I'll check to see it they have a sandblasting gun nozzle there too.

Well, I have been blasting and powder coating for several years now and can say that I have never seen this. I use Eastwood products but have never used the chrome. I blast and preheat, then cool and then coat and into the oven at 400 for about twenty minutes. Never had any flow issues or orange peeling. May be that I have been lucky.
I blast with a 3hp ingersol 100 gallon tank. I use glass bead almost always and real fine. Never have any big issues here. I do change the media each time that I replace the blast screen on the site glass. And I have real dry air. Very important. A little moisture will screw up the works quickly. I drain the tank frequently and the water traps in the line. I blast at 70psi with the fine media and it seems to work out pretty well.

The chrome that I'm working with says I need to cure at 375 after flow out and also states that it is not recommended to preheat above 375 degrees because it will cause discoloration. What I also found weird was, after I did one coat, I took it out and put a clear coat on it. When I sprayed the clear powder on, it was a white looking powder so you can see the how the powder sticks, it sprayed on with pits on it. The piece was nice and cool at this point and had just been pulled out of the oven. There where no oils on it or dirt. What causes that?

 

[bobs409]

Buy the fine sand, not the medium. I just did some blasting and got the Quickrete medium. What a joke! The stuff looked like the bottom of the barrel and this is not the first time that happened. Sand sizes ranged from big, medium and powder! : After I screened it, I ended up throwing half of it away as it wouldn't go through the screen. Also, it felt like it was "rounded" rather than having sharp edges.

I got some of the same brand but fine grit and it worked alot better!

Sandblasting sucks big time. Even the pressure type blasters seem to take forever.

 

[3483x2]

Your latest description sounds more and more like moisture is in your lines.

Pitting (clumping) should never occur while applying powder.

Check for:
1) Your powder media is dry
2) Clumping or caking of powder at your source.
3) A solid ground to your product
4) Moisture traces from your compressor or lines

When appliying your powder, it should lightly "dust" the product before flowing and curing.

If any moisture is present, you'll never get to any acceptable flow cure stages.

On another note, I never favored sand as a blast medium.
Glass beads is a good "middle-of-the-road" media for stripping auto parts.

If you still have problems, post a pic of your results if you can. From there, we can better guide you.

 

[fastcars]

What I did with this piece is I powder coated it, got some orange peal but I was willing to live with it so I decided to put a clear coat of powder on it, thats where the problem occured. Here is a link to 8 pictures I took, they can be enlarged to sho detail so you can see what I'm talking about. The link will open in another window.
http://picasaweb.google.com/lmnop1977/2009_06_08?feat=directlink

 

[3483x2]

I could be wrong, but it looks like you could be suffering from "outgassing"

Aluminum is more prone to this condition than metal, but we must be wary of both.

The cure for this is to (following stripping):

* heat your product unpowdered
This bakes out any microscopic vapor in your product
* Mildly cool
* apply your powder
* flow (250 degrees)
* and cure (350 - 370 degrees or per mfg suggestion)

Still, I'd check your powder gun source first since you mentioned pitting during your application process. (a simpler check)
Clean your lines, and try a scrap part to ensure you can get your result before stripping your product.

Either way, it's clear moisture is affecting application process somehow.

 

[dq409]

Also, some blasting cabinets like a little less pressure.
Give that a try and see if the flow improves.

 

[3483x2]

"What I did with this piece is I powder coated it, got some orange peal but I was willing to live with it so I decided to put a clear coat of powder on it, thats where the problem occured."

I re-read this and realized your decision to clear powder over your chrome color.
Sorry I missed catching this action before.

Once this base coat is cured, applying a secondary coat over the base would tend to pit or clump since the base seal is already complete.
i.e. The second coat having little to bond to may very well be the reason for your issue.

Be aware that powder coating fundimentally keys off an electro static bond to the base product.

Applying clear over an already powder coated finish is nothing like simply applying a clear coat over a painted surface. no1:

This is not to say it's impossible to do, but applying the second coat to an already powder coated surface is more of an advanced technique.

I would consider re-stripping your product, mind your moisture content, and go with just the base chrome powder.

With improvements to your flow and curing technique, you shouldn't have to apply anything over your base chrome.

 

[fastcars]

I wet sanded and sprayed clear on the piece again. this is what it looked like. I wont use clear again. I'm just going to blast it again. powder it chrome without clear coat. So how do I do a second coat of chrome if the first coat isnt thick enough?

 

[3483x2]

"So how do I do a second coat of chrome if the first coat isnt thick enough?"

Sorry to say that comes with experience.
Basically, you "dust" your product as saturated and evenly as possible.
Just make sure it's thick enough so you don't have to re-apply. 3 mills thick if memory serves.

During the flow process, the powder should then evenly spread and bond to the surface. This is where a good ground during application benefits your results.

BTW - How are you drying your product following wet sanding?
Could this be your moisture villian?

Your surface must be truly dry, before dusting or outgassing will occur.

This is why blasting is a better process, since it results in a "chemically clean" product.

Hang in there, powder coating IMO is still the way to go.
It'll come.

 

[fastcars]

Well, after wetsanding it the first time I just dryed it with a paper towel and powdered again. That didnt come out so good. This last time, Where you see the last pictures of the powder on the part, I dryed it with paper towels then cleaned it with acetone. After I took those pictures I put it in the blasting cabinet again to redo. Right now I have the second a-arm in the oven curing. All I did to that one was blast it, blew air to dust it off, and cleaned with acetone.... I also put it in the oven to go get it hot, then pulled it out and powdered it right away. I know thats not the way to do it but when I called eastwood, they told me to do that so I'll see what that looks like in about 20 minutes. Oh yea, and the guy at eastwood also told me to clean it with acetone, we'll see what the result are in a bit. Oh yea... one other thing. The gun calls for 10-30 psi, I have it set at 20 psi at the compressor. When I'm start working, I get a big puff of powder that blows out and get all over the piece. Now I start by aiming the gun away, start spraying then bring the gun to the piece I'm working on. Sometimes the puff comes out of nowhere whlie I'm in the middle of powdering, then I have to blow it off with air.

 

[fastcars]

Here is the result. Its has the best finsh so far but I have some "veins" in some spots. Looks a little like small cracks. Will these buff out? Here are the pics.

 

[3483x2]

You look like your getting it...

The first pic should be the target finish you're after throughout.
The veins are still somewhat of a weird occurance though.

Hopefully a light buffing may help, but not sure what your root cause is.

clean, clean, clean surface prep is the key.

This forum may also offer you some guidance.
I'm sure Eastwood has something this as well...

http://forum.caswellplating.com/powder-coating-questions/

 

[fastcars]

thanks for all the help. Im going to read that new forum you sent me. Looks like a bunch of good info. I'm in the process of sandblasting that other a-arm atm... tough to get off. I dont want to have to do that again. Thanks again.

 

[dq409]

Are you using an inline regualtor and moisture trap?
Does your compressor put out enough constant air pressure?

One mistake that is common is the use of a too small compressor that can not keep a constant pressure.

The small compressors can`t keep the pressure constant and the pressure will drop below the recommended pressure as soon as you pull the trigger on your spray gun.

Just asking,,

 

[fastcars]

I have a regulator. I think its an inline regulator. I hooked it up on the compressor outlet, then hooked up the filter right after it, then the hose... I also have a little disposible water trap at the powder gun. I have a 7 1/2 hp compressor. I find it strange that I put the regulator to 20 psi, then when I use the air the pressure on the regulator drops a little. I'm guessing thats normal?