Clear Coat Peeling Away, Need Help !

[pauliemc]

OK. this one has me stumped.

Im using automitive clear. 2K. with a hvlp gun. Same setup as I have been using for the past 3 years with no problems at all. But for some reason the clear coat that I put onto 2 guitars this month just peels off. Its almost like taking a jacket off of the body, there seems to be no adhesion to the underlaying surface. twice on one, & about to be 3 times on the other if it fails again today.

I figured it may be a conflict between the base coat colour paint on one guitar, But the second is not coloured & the same happens there. I have tried samples on scrap & they are fine. you need a sander to get it off. but on the guitars it just wont stay put.

Anybody had this before ? any advice ?

[Ripthorn]

Was there ever any presence of silicone in your shop near these guitars? Otherwise, it is a conundrum indeed.

[John Abbett]

Hmm, that's a tough one.

Is it a two part mix? Maybe grabbed the wrong catalyst?

Was it cold in the shop when you sprayed? Shouldn't cause that drastic of failure even if it were.

Failure on bare wood on one? It's got to be something in the clear. Sounds like it's missing something.

[WezV]

have you done any grain filling, sealing or wiping down with anything else? did you do the same process on the scrap you tested on

[westhemann]

You need to sand between coats with 2k..there is no burn in once the base coat has cured,so there is nothing for it to grab.

I use 320

[demonx]

Please layout your complete process, including what products up to what gun pressure you're spraying at. Sanding process, flash times, everything you can think of.

The more detail you tell us the more we'll be able to help isolate the problem.

Be it prepsol not wiped off, hardner failure, inproper sanding process... just tell us everything.

Cheers

Edited October 26, 2011 by demonx

[pauliemc]

OK. This is the stuff I used here =30608&tx_vossnew_group[action]=show&tx_vossnew_group[controller]=Group&cHash=6c7653c61d3c89b6a46d32bd34a89cd5]My link

I have used it on many guitars like this.

01) sanded to 320,

02) left to hang in 25degree C to acclimate for 24 hours.

03) cleared off with air @ about 60 PSI. then applied primer.

04)scuffed to 320 after 24 hours drying. applied clear coat with colour additive

05) wait about 5 mins & apply second coat.

06) leav for 72 hours before applying top coat of untinted clear.

07) wait 5 days then begin polishing

I use a graco finex gun with 20 psi reading at the gun when the triger is pulled.

This is exactly the process used on the first guitar with a blue tint. but when removing the masking along the fret board after step 06, the finish just lifted with the tape. like a jacket around the whole guitar.

The second guitar did exactly the same. the only difference was that it had no primer or colour tint.

The exact same process for each guitar was done on scrap testers & they are fine. I used compressed air to clear off the guitars before spraying, not solvents or pre-paint.

The hardner & coat come attached to each other, so you cant get the wrong catalyst.

Im not sure about silicon ? i doubt it, but it would make sense i suppose. I must look into that.

This was a new batch. freshly opened pack. never havin had this trouble before Im thinking it may be a bad batch

Either way. havin to re-apply a finish to 2 guitars for the third time is an absolute pain in the ass

[John Abbett]

Thinking it might be a bad batch.. But here is something to think about.

Take a white rag, and blow your air compressor into it for a minute. See if the rag has any oil on it. Does your compressor use oil? Maybe you've blown a ring and it's putting oil into your air stream. Your process is to blow the dust off before the coats.. It wouldn't take much oil to cause a problem.

-John

[demonx]

A few things that stand out:

Do you run oil/water traps on your airlines? Do you keep them clean. Do you also drain your tank tap every time you spray until no water sprays out? Its not so much of an issue with water based paints but with 2k auto paint, can be a disaster.

I dont bother to let guitars aclimate before I spray - but thats a non issue. I just spray under heat lamps if it's a cold day. I let it sit under the lamps for about the time it takes to mix my paint. With that said do you let the clear/primer sit for a bit before you spray for the hardner in the product to "activate" as some people call it? I was once told by a paint tech that if I mixed the paint first before I assembled and set up the gun, thats just enough time. This is only for primers and clears as they have a hardner.

Spraying off with 60psi will not clean the guitar proper. I airhose them off at 120psi @ 16.5cfm - THEN tack rag the dust off as the 120psi is not even enough. I do not air hose in the same room I'm going to spray in as thats more dust floating around. Maybe the fine layer of dust could be causing failure.

Since I'm not sprayig in a booth I usually leave primer for more than 24 hours, but 24 hours should be sufficient if you're using a fast hardner. I like to leave it until I cannot smell the chemical in it. With cars you dont get primer sink as the metal doesnt absorb the paint, with guitars you can get the paint to sink into the timber over time. One guitar I've painted is hanging behind me in primer for its second week now before I sand it and reprime. Paint is a game of patience. It'll look perfect for 3-6 months, but years later it'll sink into the grain. Waiting is an attempt to prevent this.

COLOR ADDITIVE... I've been caught out here in the past with additives to clear. Even when in the tech sheets they say you can, I've had product seperation from these. You spray it, looks perfect. Keep all the layers etc, still looks perfect. See it the next day and its a disaster. These days I keep clear as clear and let it cure for a week or more, sand (to 600) and spray trans color layers, usually candy dies mixed in a basecoat blender or an over thinned basecoat, let it cure for a couple hours then spray pure clears again without sanding.

FLASH TIME... 5 minutes with automotive 2k is way too short unless you're in a booth. You cannot follow a tech sheet for flash times if youre spraying in air rather than a booth environment. I usually spray a tach coat of clear, wait 5 minutes, spray a full coat, wait 10 minutes, full coat, wait 20 minutes, full coat, wait 40 minutes - doubling the flash time each coat as youve changing the spraying environment, hense youve changed the way the chemicals flash and react. If you're only leaving 5 minutes per coat and youre spraying several, what can happen is it'll cure on top and the underneath layers are still reacting. This usually causes solvent pops etc, but it can also cause complete failure like blisters, extreme ripples (blisters in sheet form)... I've experienced this on a car in my earlier painting days. Really sucked, simply cause I didnt leave enough time between processes.

TOP COAT OF CLEAR... you cannot leave auto clear that long and then just spray another coat. It'll need to either sit around for a week or so (until you put your nore on it and not smell chemical) and then sand before spraying, or you just spray enough layers in the previous step and then cut/polish. Obviously this cant happen if you're using additives in the clear, but I suggest that the easy way is not always the best way.

I hope at least something here can help you out.

Cheers

[demonx]

These pics are from some Corvette Stingray grills I painted with an unfamiliar product.

Does your failure look anything like this?

In the second pic you can see I took a razor blade and sliced open one of the blisters to see the exact layer where the failre was occuring. As you can see it's the green epoxy primer as it's on both the upper and lower part of the blister.

After having a PPG rep come to my workshop and using some electrical devices to examine and measure the paint thickness I was told that my cure times were not long enough for the paint product. I said on the tech sheet it said 8 hours, I'd left it for over 24, so I was being over cautious - he explained it needed 42hrs even though the tech sheet said 8. He explained the tech sheet is only a guideline and dont pay too much attention to it!

After this I've always left that product for 2 days before spraying over it and never had a problem with it ever since.

Something similar to this may be whats happening to yours ???

[pauliemc]

Apart from the blistering, this looks almost exactly what im getting. just peeling away like a skin. But its not only happening on the guitar with the primer. Its lifting away from bare timber aswell. thats the part that realy has me stumped.

But I rekon you may be on to something with the time between coats. I only wait 3 days before scuffing & spraying the top coat. I dont use a lot of heat to cure either. Although I only ever put on 2 coats at a time to avoid overly thick finishes not being able to gas off properly. But there is a very distinct smell from this stuff & I can still kinda smell it 3 days after applying it - when Im applying the final coat.

Iv never let finishes sit for a while before spraying, sounds interesting. I must give it a try.

my compressor is drained daily, probobly overkill. but its done before I spray anything aswell. I run traps in the lines, & do check them weekly. They seem fine just now.

[demonx]

A rule I learned from a guy who owns a paint warehouse distribution company has won more car "best paint at show" awards than what I've owned cars is "do not sand it if you can smell it". He say's he usually leaves cars sit for 3 months before sanding the clear. The longer the better he said. I wait a week or two as I'm not that patient, but unlike him, my paint jobs dont start at $40k if you get my drift!

From what you describe - I'm convinced its the combination of flash times, possibly spraying too thick layers and not waiting long enough before sanding and doing recoats.

Make these adjustments and see if your problem dissapears. If it is, its an easy fix and one that'll help you for years.

Cheers

Allan

P.S. After I made those adjustments I mentioned in the previous post (ie: leaving it for 2 days rather than just overnight) heres what the end result turned out like. No bubbles, blisters or anything. Just nice smooth perfect paint sprayed in the same shed I build my guitars in!

Edited October 27, 2011 by demonx

[pauliemc]

Thanks Demonx. Info very much appreciated. You collegue's scratch n sniff method seems a good indicator of when to progress from one stage to the next. Dont scuff it If you can still smell it

I think I will strip both of these back to bare wood today & start from scratch. I rekon it might be about a month before I get anywhere near finished but screw it, iv already wasted more than that on these as is. Ill throw up aome piks of them when done, just for the hell of it.

P.S. Love Corvette. Have my eye on a C2 at the moment.

[demonx]

I'd love a C1 or C2

I've had two C3's, a 76 coupe and a 70 vert, but they're both gone and I've got a 57 4 door chev. Love it!

Make sure to post updates when you get this stuff sorted and let us know what worked and so forth

[ihocky2]

Dumb question, but are you mixing components from any other companies for anything at all. Even using die or pigment to mix to get your color or Brand X primer and Brand Y basecoat? Some just do not play well with others.

I don't think it has anything to do with your problem, but why are you spraying at 20 psi with a low pressure gun? I run my conventional at 25. I have a Finex 1000 and I have to run my compressor around 70-80 psi to get it to run at 5-10 psi with the trigger open. At 10 PSI with the trigger pulled it's like a hurricane coming out, I can't imagine at 20. I would think you would getting organge peal problems from that much air.

[demonx]

I spray base and clear coats at 30psi gun reading with a 1.4 tip and primers at 35 psi with a 1.8 tip and fillers (not on guitars) with a 2.5 to 3.0 tip at 40-50 psi

Usually my compressor is just set at 125psi and I use an adjustable gauge set at 30+ which is screwed into the gun.

Any lower and even though it seems like you're spraying, the paints more falling out than spraying out.

You're meant to move quick, if the paint is spraying out proper and you move slow, you'll have product running everywhere. If you have the psi set too low the paint will not atomise properly (with auto 2k, I cannot comment on other paint systems)

Edited October 27, 2011 by demonx

[pauliemc]

Dumb question, but are you mixing components from any other companies for anything at all. Even using die or pigment to mix to get your color or Brand X primer and Brand Y basecoat? Some just do not play well with others.

I don't think it has anything to do with your problem, but why are you spraying at 20 psi with a low pressure gun? I run my conventional at 25. I have a Finex 1000 and I have to run my compressor around 70-80 psi to get it to run at 5-10 psi with the trigger open. At 10 PSI with the trigger pulled it's like a hurricane coming out, I can't imagine at 20. I would think you would getting organge peal problems from that much air.

I dont mix manufacturers products, I used to. but I got some funky results so I just dont bother anymore.

As to the air pressure. My gun seems fine at 20 psi on the trigger. but having said that, iv never tested the gauge on the tool end on the line so it may in fact be lower. I dont tend to get orange peal, seems fine.

You say yours blows like a hurricane ? mine doesent even start to cloud the room up. Although I have a similar gun from iwatta that would absolutly destroy the place at the same pressure. I might strip it totaly this evening & have a look later

[ihocky2]

The pressures could just be the difference in the model of the gun. Like I said, mine is the Finex 1000 which is the mini gun. I run a 1.0 tip for base and clear and am going to pick up a 0.8 for detail work. The gun is rated at 100 psi max and 10 psi max at the air cap. So I would guess that you are using a larger gun.

I can tell you for certain that if I slow down at all I get major sags and runs in the paint, so I am getting plenty sprayed on. Once I figured out my settings I could get away without wet sanding and go straight to polishing if it was a car. My guitars I like a dead smooth finish, but most days I can get away starting at 1500 or 2000 grit, just to get the slight imperfections out.

[Kammo1]

Bro DemonX has raised some fantastic points and from my experience he definately knows what he's talking about so read and read again and absorb what he has stated. Any automotive clear if it has had 24 hours or more time to elapse between coats needs a mechanical bond which means sanding with the appropriate grit generally if I'm down to the clearcoat stage I sand with 800 grit and I literally remove all the shine on the guitar so its a dull matt finish. Then I even go over it with an Ultra fine grey scotchbrite material to get any small divets that are below the level of the clear to a dull matt finish as doing this with paper is almost impossible without sanding the area to the level of the imperfection. After this I take 2 rags ie microfibre one with the degreasant cleaner the other just to dry it and wip it off "DON'T" let the cleaner allow to dry on the guitar body always wipe it off with the clean rag. When this is done use your gun or a blowjet and blow off any lint or other foreign bodies of the guitar and then spray a light tack coat allow flash off time and then a full coat and go from there. It defiantely seems to me the reason for loss of adhesion is the mechanical bond problem where the clears has absolutely nothing to grab hold of. Hope it helps and again as mentioned above patience and cleanliness is the key to a perfect sprayjob.

[pauliemc]

Some piks of this one polished & assembled. Should realy be in the original build thread But I cant seem to get that thread to work for some reason.

I will put up some of the back & neck over the weekend. I think it came out pretty cool - even if I do say so myself

[demonx]

Looks pretty cool. Blue and white just work so well!

I'm digging the fretboard end, looks very much like a BC.Rich Bernie Sr Commemorative model which were very big buck guitars (not sure what other brands do this but I know I liked it when BCR did it.)

Dont know if I like the rear binding, but seeing the back of the guitar might make me change my mind.

On the upper stripe near the neck side strap pin, was that when you peeled the tape back? I once was taught a trick to stop that happening by peeling the tape back over itself. It's supposed to help. Some people say that peeling it back while still tacky helps this also. If you had've noticed it before clear you couldve just taped the are and shot it very lightly with the airbrush to hide it. I've had to do this several times, both on guitar and on a car. I really hate cleaning my airbrush though but they are so handy for fixing stuff like this. Still looks awesome though. If the customer asks just say, you get things like this on handmade guitars, makes them stand out from the chinese ones!

[pauliemc]

On the upper stripe near the neck side strap pin, was that when you peeled the tape back? I once was taught a trick to stop that happening by peeling the tape back over itself. It's supposed to help. Some people say that peeling it back while still tacky helps this also.

Got it in one. I peeled the tape from the bottom end toward the neck & that little spot went to crap. I was gona set up to fix it, But the customer didnt care.

There were other little areas that were not spot on, Like the stripe to binding transition on the back. & a little run over of the black by the neck on the top bout. But he did not want them fixed. rekoned we did good to save it at all. Just happy to have Gods Hammer back in action.

(its been dubbed Gods Hammer as it weighs an absolute tonne, I mean properly heavy, just how I like them)

Anyway, Piks of the back.

Tried to follow the same theme here as the front. Striped like a 427 Cobra. The binding is there to mirror the front & keep the white stripe thing going. Left the sides unpolished aswell. so they stand out more from the blue front & back. Also to get that kinda rough black finish you have with stone chip finishes on the undersides of some cars.

[Maiden69]

TOP COAT OF CLEAR... you cannot leave auto clear that long and then just spray another coat. It'll need to either sit around for a week or so (until you put your nore on it and not smell chemical) and then sand before spraying, or you just spray enough layers in the previous step and then cut/polish. Obviously this cant happen if you're using additives in the clear, but I suggest that the easy way is not always the best way.

I hope at least something here can help you out.

Cheers

This may be one of the reasons. I tried as much as I can to use the same brand products when I'm painting, but if I can't I make sure I read the product description to make sure that I can paint in the same way I always do, or if I have to make any changes. Once I finish prep and seal, it's game on till the last coat of clear is shot. This is with 2K only. From base coat to the last coat of clear is shot in the same day, within minutes from each other coats.

As far as gun pressure, it all depends on the gun you are using, mines are regular guns, so I run them at close to 45, but I have used some that run at 12 and flow the paint very ncie.

[pauliemc]

Stripped this one & polished the hell out of it. Reassembeled then hit the camera man up for a few piks. I may just have to GOTM this one - hated having to give it back to the customer.

[ScottR]

Stripped this one & polished the hell out of it. Reassembeled then hit the camera man up for a few piks. I may just have to GOTM this one - hated having to give it back to the customer.

Congrats on the GOTM win Paul!

Scott