Hi guys, I sprayed some Axalta basecoat on Thursday. Do I need to re-scuff before clearing? It's a solvent based basecoat. If I need to re-scuff, I'm thinking a gray scotch pad and apply more base and then clear?
Is that Cromax Mosaic that uses a dedicated basemaker? That basecoat supposedly you reduce 200% to spray. I just looked at the tech sheet and it says you can denib and just respray more basecoat before clearing. It also says a maximum of 24hrs for clearcoat.
I called Axalta tech line, they told me after 24hrs, the base coat ( Axalta chroma base) should be scuffed with 600+ grit re-based and then cleared within the 24hr window. This is a rocker panel cover molding, I took my chances and applied two wet coats of Universal clear....see what happens I guess.
in the tech sheets for every base i have ever seen they give a 12-24hr window for clear. it takes this amount of time for all the tail solvents to come out completely and the base to harden up. the thing is, base is not a crosslinked product. it has no chemical resistance. you can base something out with any brand out there, let it sit 6mos then wipe it off with lacquer thinner or reducer. it bites right into it. the solvents in the clearcoat will do the same thing. i think the tech sheets give the 12-24hr window to relieve them of liability if the painter lets the base sit 2 weeks then dry spray their clear on over it. in that instance yes you would have delamination issues. when you are out of window, use the slowest activator you can get away with, add 10% of a slow reducer and spray med wet coats. you will be fine.
My understanding as to why as told by a Chemist friend, is their addition of Paraffin Wax in the Base formula. I tested it 8 different ways from not sanding, sanding and tacking, sanding and wiping down with water rag, wiping down with water/soap rag, scotch padding etc. then recoating and clearing. In every instance where it was sanded and rebased and cleared when I took a piece of tape and pulled it delaminated at the rebase layer, just like the Chemist friend said it would. It went against everything DuPont and my Reps have said and always told me. When I did the test I was going to Training and I took that panel with me and threw it on his desk before class started and asked "can you explain this?" his reply was what I was told he would say "you must have done something wrong".
You can feel the wax in the mix. Do a test panel, scuff it and run your hand across it, it has a waxy feeling and nothing will stick. I was told that as it flashes off there is a micro layer that comes to the top allowing the next layer to adhere but will be removed when sanded exposing the wax under it and any additional layer of base or Clear will delaminate.
I brought it up to my paint jobber and after I explained what I did and asked what he knew, he said without me interjecting said "Paraffin wax?".
Why is paraffin wax added to base?..is it added to all base coats? So if base sits too long, just clear it anyway? Or strip down to primer and rebase and then clear? What is maximum amount of time you can apply clear coat over base, and why do some base coats have a longer window for this then others?