Second coat problems

[Guest]

So I've had a tough weekend re-doing parts for what I beleive to be shop air contamination. I sprayed a bunch of parts wet black. Some of them turn out great, others have 2-3 fish eyes on them. I can't for the life of me figure out where they are coming from. All the parts are new chrome. I sanded/scuffed with 400 grit. Sprayed/dried with DeAlcohol and used the torch. I sprayed 4 parts at once, only one had the fish eye.

I think I have shop air contamination. I'll be buying new filters for my desiccant dryer system tomorrow and see if it works. I just hope they have them in stock.

But here's my issue, I scuff up the bad coat for the next coat adhesion with a maroon scuff pad. Spray and it turns out all shitty again. Its not fish eyes this time but it looks like someone took a pin and just barely touched the surface a few hundred times. This isn't the first time Ive seen this, I see it on just about ever reshoot that I've ever done. Its just getting to me now and I have to ask. To make the matters worse they came out a little more orange peeled than I think is acceptable.

Guess I'm putting the cybersolve I received on Thursday to good work already.

Thanks everyone, Rob

[Streetwerkz]

Re: Second coat problems

I have one of these at the end of the line just be for my Powder coat gun.
It made a HUGE difference for me years ago on my cnc plasma in terms of cut quality, so I adapted it to my powder gun have not had any problems with water or oil.

http://www.harrisweldingsupplies.com/in ... ProdID=668

An auto drain for you compressor will go along way also, hard to remember to drain the air tanks several times a day.
just install in the bottom of your tank, plug in to the wall and pipe out side

http://www.compressorworld.com/drainvalves.aspx

[Guest]

Re: Second coat problems

I know it's metal but did you outgass? Chrome is a pain sometimes with oils or polishes/wax to get clean. Did you clean it with any degreaser or a wax remover. Do you have any pics?

[rbroker]

Re: Second coat problems

I didn't out gas any of the parts, just used my normal cleaning routine that I always use. All are steel parts.

All the parts I'm having problems on have been chrome until last night when I shot some mirror white and it had 2 fish eyes on it. I was able to use L2P and cover those luckily.

It has to be shop air. I use a Sharpe Dessicant dryer system. I've owned it for about 16 months, and yesterday was the first time I checked the filters on the water and oil traps. Both looked saturated, but then again, maybe they come with a yellow tint....

I'm afraid to reshoot this long heat shield. I don't want it come out with "pin" marks on it. Its probably best to strip it down to bare metal again. I don't want a questionable quality part leaving my shop. bad news travels fast.

[Guest]

Re: Second coat problems

I didn't out gas any of the parts, just used my normal cleaning routine that I always use. All are steel parts.

All the parts I'm having problems on have been chrome until last night when I shot some mirror white and it had 2 fish eyes on it. I was able to use L2P and cover those luckily.

It has to be shop air. I use a Sharpe Dessicant dryer system. I've owned it for about 16 months, and yesterday was the first time I checked the filters on the water and oil traps. Both looked saturated, but then again, maybe they come with a yellow tint....

I'm afraid to reshoot this long heat shield. I don't want it come out with "pin" marks on it. Its probably best to strip it down to bare metal again. I don't want a questionable quality part leaving my shop. bad news travels fast.

Why dont you run down to the local parts store, hardware, or paint supply and grab a desicant filter to screw on your gun. Like this.
http://www.eastwoodco.com/shopping/prod ... uctID=1800

[rbroker]

Re: Second coat problems

I have one of those inline already. Its possible its spent though...

[Auto-Cycle PC]

Re: Second coat problems

Sounds to me like back ionization. Black is the worst color for showing the pin holes caused by BI. Colder less humid conditions make the problem worse. If you have an adjustable gun you need to turn the voltage down as low as possible and increase you powder flow so you can back away from the part to around 15 inches or so. You will use a little more powder when this happens to resolve it unless you spray warm.

[rbroker]

Re: Second coat problems

I didn't see any craters when spraying, they looked flawless. I've been making an effort to hold the gun further back, but I'll try the voltage thing too. I try to shoot powder as low as I can, like 20kv range. Any more than that the stuff sticks to my face like a mofo. I only turn it up if the directions recommend it.

100$ bucks for replacement filters . I'll also change my inline filter too.
In my mind since it happened on the white last night, it has to be the shop air.

[ATL Powder]

Re: Second coat problems

It may not help in your case, but I have found that shooting a primer over the subtrate (regardless of whether it is stamped steel, chrome or cast) prior to shooting a mirror or wet black, almost always eliminates these problems. Just one more suggestion.

[Smashing]

Re: Second coat problems

Good luck with the new filters! Let me ask - what instructions are you referring to when you lower your voltage??

[rbroker]

Re: Second coat problems

Some powders on pbtp recommend a Kv setting, like silver vein for example was 60-90 kv...

I spent the night attacking everything in the garage.

I first added 20 feet of copper pipe to my shop line via one of those flexible copper coils. Added a 5th drop point. Added a water trap filter further down stream about 15' from my gun, then another disposable filter at the gun.

I'll install the new Sharpe filters tomorrow when they arrive. I can't believe they run over a hundo for the two filters. If that was advertised I would have bought the Devilbiss unit instead. Doh! live n learn.

I'll spend tomorrow night shooting test panels all night to ensure the problem is solved. If its not I wasted almost 200 bucks

[rbroker]

Re: Second coat problems

Well I think I solved the problem. I guess the test will come in the coming days. I sprayed 7 4"x5" panels in wet black last night all at the same time and not one had a fish eye....

Cost a lot of money, but so does redoing customer parts for no good reason.

Thanks for the help, i'll post back if it still works.

[JW450R1]

Re: Second coat problems

i agree with auto cycle.sounds like back i.i have been going threw the same problems.go buy yourself a humidity gage,and you will see a difference.

[rbroker]

Re: Second coat problems

It works again!! Those Sharpe filters must have been shot. Its wierd that they work one day but not the next. Shot a bunch of parts in wet black last night and no fish eyes.


As for the second coat problem, It'll take time to fix that and try new techniques. Thanks for the advice everyone.