etch primer

[gazza]

G'day all I have painted the fire wall of my car in etch primer.Do i just sand back the etch primer and paint the top coat or do i sand the etch primer then put on grey primer then sand and top coat.I have not used etch primer before it is all new to me.Always used grey primer.Cheers Gazza.

[bootlegger]

It depends what etch primer you have used. Generally you need to use a primer over it compatabke with the paint. Ive painted straight of epoxy etch primer no problems. It doesnt fill very well though.

[toey1977]

if you've used a standard 1k etch primer you can apply like a wet on wet set up which is apply one to two coats of etch then apply the primer straight over the top just allow a standard flash off time in between coats then you will only have to sand once before top coat alternatively you can do the same and if there is no repairs done on the firewall you could use a wet on wet primer straight after the etch then paint top coat directly onto the primer after a standard flash off time some 2k primers specifically have wet on wet primers although you can get similar result from a acrylic primer just by over thinning it if your not sure what i mean wet on wet basically means your painting while the primer is still soft and able to accept another coat of primer but your using paint (colour) the paint can then bite into the primer and gives good adhesion down side is some wet on wet primer set ups in 2k (cheaper brands) can reduce gloss level of the 2k clear or top coat but a quick lick with a buff fixes that and yes i will only use 2 pack paints but the same method works for acrylic hope that helps

and after all that to answer your question you should prime and will need to sand but next time best to prime wet on wet over the etch.
etch primers are very porous and can allow moisture to penetrate

or etch then epoxy the body gives a great sealing coat and great adhesion

[rosco]

Hi, I've always tried to apply the etch primer "wet" - but not to the point of running.
I leave it the suggested time (depending on paint type) - then try not to touch it before applying primer.
As far as I'm aware - the etch primer will "bite" into the metal... and I've also used it on filler - it's the "bonding" layer between primer and substrate.... it will not seal - nor will the primer (unless it's 2K - which I refuse to use)...
With the acrylic system - it's the top coats which seal.... 2K is a totally different system... I'm not sure on enamel - but I believe that requires the hardened top coat to seal the layers..

I do sand etch primer if the pattern produces runs, marbles or sandpaper effect.... but only enough to prevent the faults showing through following coats ....

Hope that helps.

frats,
Rosco

[gazza]

G'day to all.thanks for the advice on the etch primer paint. i will sand it back and spray on 1k filler primer sand it back and then put on top coat and clear.I am using acrylic paint.Cheers Gary.

[rosco]

Gary, if the surface is reasonable - I would just lightly sand it to create a "key"... rubbing too hard might lift it away from the metal...
If it needs work however - and you break through... you can spray another wet coat over it.... but I would also "key" up all the previous 1K etch....

frats,
Rosco