Pinholes appearing where primer has been
Discussion
Sorry if this isn't exciting for anyone outside of the bodyshop trade, but I'm just posting it up to see if anyone else he has this problem.
A couple of weeks or so before Christmas, we've started having a problem in the occasional job of pinholes appearing in finished jobs, but only in patches where the primer was. The rest of the panel that's just had paint and lacquer is as it should be.
We use Octarol/Valspar 2K primer, 2 light coats, let it flash off for 10 mins in the booth and then bake it, and/or leave it overnight. Then wet flat with 800, before drying the panel out and painting. Approx 24-25c temp for spray, then 65-70c bake for 25 mins.
The panel looks great when first lacquered, but after bake these microscopic pinholes are appearing in the lacquer where the primer was underneath.
We use a solvent paint system. All Octarol/Valspar.
Any ideas?? It's driving me nuts at the moment!
A couple of weeks or so before Christmas, we've started having a problem in the occasional job of pinholes appearing in finished jobs, but only in patches where the primer was. The rest of the panel that's just had paint and lacquer is as it should be.
We use Octarol/Valspar 2K primer, 2 light coats, let it flash off for 10 mins in the booth and then bake it, and/or leave it overnight. Then wet flat with 800, before drying the panel out and painting. Approx 24-25c temp for spray, then 65-70c bake for 25 mins.
The panel looks great when first lacquered, but after bake these microscopic pinholes are appearing in the lacquer where the primer was underneath.
We use a solvent paint system. All Octarol/Valspar.
Any ideas?? It's driving me nuts at the moment!
paintman said:
Are you using a basecoat followed by clear?
If this has not happened before what changed immediately before the problem appeared? New batch of paint/thinner/primer/hardener/conditions in workshop?
Pinholing or solvent popping are well documented in various paint manufacturer's websites & the causes given are trapped solvent, air or water.
That it happens only on the primed areas would suggest that it's either water in the primer or trapped solvent & I wonder if the solvent in the topcoats is penetrating the primer & becoming trapped by the top coat during the baking process only to work its way out later. How are you baking?
Have you raised this with your paint supplier or with Valspar & what was their response?
Be interested to know any other experiences of this & the solution.
Hi guys,If this has not happened before what changed immediately before the problem appeared? New batch of paint/thinner/primer/hardener/conditions in workshop?
Pinholing or solvent popping are well documented in various paint manufacturer's websites & the causes given are trapped solvent, air or water.
That it happens only on the primed areas would suggest that it's either water in the primer or trapped solvent & I wonder if the solvent in the topcoats is penetrating the primer & becoming trapped by the top coat during the baking process only to work its way out later. How are you baking?
Have you raised this with your paint supplier or with Valspar & what was their response?
Be interested to know any other experiences of this & the solution.
Edited by paintman on Thursday 5th January 23:35
Thanks.
We always use the booth air supply to prime to ensure it's clean/dry air. Our air system is a Kaeser compressor and dryer unit, then into a moisture trap then into a bank of triple Devilbiss spray filters, I think they are called FLRCAC-1. The filters are all around 12-18 month old so I'm hoping they are still doing their job ok.
The only things that changed right before the issue was a new 5 litre tin of Octarol thinners (used for primer, base and clear) and the weather went suddenly cold. But nothing else changed.
We bake primer at 60c for 25 mins then leave it it at least a couple of hours, sometimes overnight. Then wet flat with 800, dry it off with blue roll, leave the panel in the booth on 24c spray for 10 mins while mixing paint to warm the panel, then paint solvent basecoat (Octobase), then allow 15 mins or so flash off before going with the Octarol clearcoat and very fast hardener.
Yes, raised this with supplier and Valspar/Octarol and have basically been told to follow the instructions for the products... which of course we do.
It gets stranger.
Tried a different primer. Same thing happened.
Did a load of spray out cards.
The ones that contained the lowest amount of thinners and the highest amount of hardener in primer contained the most pinholes after painting, clearcoat and bake. 3:1 with 0-10% etc.
The cards that were 6:1 with 20+% were almost perfect.
But why??? Painting cars sucks! Lol
Sometimes you think nothing has changed and then stuff starts reacting or going wrong for no apparent reason.
Tried a different primer. Same thing happened.
Did a load of spray out cards.
The ones that contained the lowest amount of thinners and the highest amount of hardener in primer contained the most pinholes after painting, clearcoat and bake. 3:1 with 0-10% etc.
The cards that were 6:1 with 20+% were almost perfect.
But why??? Painting cars sucks! Lol
Sometimes you think nothing has changed and then stuff starts reacting or going wrong for no apparent reason.
It's the whole primed area, but the pinholes can seemingly vary in density across a large area of primer such as the bonnet that went bad. Some patches look fine and other patches look more 'holey', but generally it's across the whole primer area and stops as soon as the primer area does.
Thanks paintman, you've been really helpful.
My head spraypainter has been doing this nearly 20 years and it's got him stumped.
We need our own bodyshop issues/chat thread
Thanks paintman, you've been really helpful.
My head spraypainter has been doing this nearly 20 years and it's got him stumped.
We need our own bodyshop issues/chat thread
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