February 18, 2015 at 2:53 am #48276
I’m currently fixing a peeling hood that looks like it was a new hood. The base did not stick to the sanded primer. I have never seen this before.
I originally thought someone had done wet on wet sealer and didn’t let it flash long enough or let it go too long. I razer bladed all the paint off with ease. I usually don’t razer blade and chemical strip because I find the paint will stick real well in alot of places and you start breaking them and gouging the metal. This hood is aluminum. I did not even use a razer blade holder, just my fingers.
I’m really curious what happened. I have seen paint fall off unsanded oem black primer, clear off the base coat, base coat off base coat, base coat off sealer that dried too long as it happened here but never base coat off sanded primer.
[URL=http://s295.photobucket.com/user/Glen440/media/IMG_20150216_0836320731_zps98fd93a8.jpg.html][IMG]http://i295.photobucket.com/albums/mm148/Glen440/IMG_20150216_0836320731_zps98fd93a8.jpg[/IMG][/URL]February 18, 2015 at 7:50 am #48280
Just by looking at the pic the substrate looks kinda too shiny to be sanded. If it is a new replacement panel the e-coat might have been lightly scuffed and base applied directly over it which is not recommended.February 19, 2015 at 5:18 am #48284
Wow! That’s crazy! I have seen this on a job we did, on a hood with clear tape. Peeled off the clear tape and the paint came off the spot primed hood. The primer was also sanded. The paint stuck over the spots that weren’t primed. I have no idea what would cause this.February 19, 2015 at 5:39 am #48286
I peeled it off under the emblem so can’t even blame the sun. The crown vics peel everywhere but not where the stickers are. Its a sun related issue with the single stage and the epoxy they use.February 25, 2015 at 7:56 am #48321
I’ve seen this once before. I believe the sanding paste used to help in the sanding process wasn’t completely washed off. I did an experiment by sanding one side of an old part with sanding paste and not washing it and the other side by sanding with the paste and washing it off properly. When I did a crosshatch test the side not properly cleaned peeled right off. There was no sign of adhesion. The other side never moved. I think it’s a prep issue. IMHOFebruary 25, 2015 at 4:02 pm #48322
That’s not a bad theory. The only problem is, in the one I seen only did it on the spots that were spot primed.February 27, 2015 at 12:53 am #48336
possibly sanded with too fine a grade ,especially if it was water based paint ,or water based that has not fully dried prior to clear coating ,but when I have had that happen i also got microblisteringFebruary 28, 2015 at 7:59 pm #48352
Whatever it was sanded with was really fine. I could not see sand scratches but they broke through every edge so they used something.
The paint had died back a bit but not really bad.
I guess could even be a wax and grease remover that left a film.March 1, 2015 at 12:24 am #48353
I still come across painters who believe the finer the sanding the better finish it will produce ,trying to explain that using 1500 when re clearing is wrong can still create arguments ,some sprayers think the scratch will show through the clear which is nonsense ,I DA back with anything from 320 to 600 for re clearing
as for base depending on if it is a solid or a metallic or pearl anything from 320 to 500 DA or 600 to 800 wet n dry ,not that I wet sand much these daysMarch 1, 2015 at 1:39 am #48354
Interesting! I have always sanded with 800 dry before re clearing. I often wondered if 500 would work, but never tried it. Thanks!March 1, 2015 at 2:35 pm #48363
I do a lot of custom work which has high build tape lines so my process is to clear with at least three coats then sand back using the DA with P400 then re clear ,I get absolutely perfect results ,remember all clear is is direct gloss but lacking any pigment and it will cover and fill the same grades as direct gloss pigmented paints will 😉 if basecoat covers P320 DA scratches as recommended by most paint manufacturers then it will certainly work with high solids clears etcMarch 1, 2015 at 2:43 pm #48364
Also the danger is when you dont use a heavy enough scratch over existing clears ,not so critical on fresh clear which will also crosslink but old stuff wont and that is where you will get delam if the clear is sanded to finely
for blow ins I can also use heaver grades but will use a foundation coat of clear base to fill the scratch ,not required for a solid colour but definitely needed for mets and pearls ,if I dont use a heavy grade I will then use P800 on the DA especially for silvers and difficult blends ,darker pearls you can get away with blue murder and I have used P400 on the DA with say Ford panther blackMarch 1, 2015 at 8:34 pm #48369
[quote=”ARTSPRAY” post=36810]I still come across painters who believe the finer the sanding the better finish it will produce ,trying to explain that using 1500 when re clearing is wrong can still create arguments ,some sprayers think the scratch will show through the clear which is nonsense ,I DA back with anything from 320 to 600 for re clearing
as for base depending on if it is a solid or a metallic or pearl anything from 320 to 500 DA or 600 to 800 wet n dry ,not that I wet sand much these days[/quote]
Very true, I would not re clear anything finer than at least 800 gritMarch 12, 2015 at 8:22 pm #48446
I did it to my hood too. I want to respray it now. Would you recommend me to use a colour protection. My friend uses one from [url=http://www.colourshield.com]http://www.colourshield.com[/url], and it look like it is a thing worth buying. What do you think?March 15, 2015 at 1:02 am #48460
dont waste your money 😉
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