Etch Primer

[jameshub]

having rubbed down my landy I had to take the wings back to exposed aluminium and just started rolling some Etch Primer on it with a foam roller.......it almost started smoking! so i'm guessing this is not a good idea.

anyone know what to use to put Etch Primer on? - I have some spray cans but they are for edges etc

maybe a normal roller will work rather than the foam ones?

cheers

[Tanuki]

Whether on Birmabright LR panelwork or on our aircraft, I've always applied Zinc-Chromate-type etch-primer by spray.

You only need to gently mist it on to give a really thin coverage where you can still just see the metal through the primer-coat. This is truly an example of where thicker is never better.

Once applied, leave it for at least 3 hours before rinsing off with deionised water. Then put in a dry environment (less than 25% relative humidity) for 12 hours before applying the primer specified by your paint's top-coat supplier.

The last etch-primer job I was involved in regularly flies at 45,000 feet and has survived inch-thick ice accretion.

[Team Idris]

And a quick dry is bad, as the phosphoric acid doesn't have time to work. That was an expensive mistake my painter made with a drying booth! The top coat of paint virtually fell off, tacking the etch primer with it

[jameshub]

And a quick dry is bad, as the phosphoric acid doesn't have time to work. That was an expensive mistake my painter made with a drying booth! The top coat of paint virtually fell off, tacking the etch primer with it

mine is just drying in a standard garage so hopefully should be ok

does it matter if its put on solid so a full coat rather than a dusting?

[Team Idris]

Yes, very much so. I rang the manufacturers for the military grade, 2 pack stuff I was using and thicker isn't better. He says 'thin' is right. All it needs to do is form an interaction between metal and paint.

I'd argue the point myself, if the proper job bloke hadn't said

I guess the thing to do is not think of it as corrosion protection. That's the job of the undercoat and top coats. (mainly shiny top coat).

[Team Idris]

I wouldn't go really thin though............

[Tanuki]

I guess the thing to do is not think of it as corrosion protection. That's the job of the undercoat and top coats. (mainly shiny top coat).

Precisely: the etch-primer is emphatically not for corrosion-protection - it's there to provide a bond between the metal and the subsequent paint-layers.

Aluminium alloys are innately self-protecting against corrosion by the way they form a very thin layer of surface oxidation when in contact with the oxygen in air. This same layer makes it hard to get any traditional paint to stick to aluminium (it also makes aluminium a pig to solder).

The etch-primer bores its way into the oxide-film and provides a 'key' for the paint to stick to.

[jameshub]

Precisely: the etch-primer is emphatically not for corrosion-protection - it's there to provide a bond between the metal and the subsequent paint-layers.

Aluminium alloys are innately self-protecting against corrosion by the way they form a very thin layer of surface oxidation when in contact with the oxygen in air. This same layer makes it hard to get any traditional paint to stick to aluminium (it also makes aluminium a pig to solder).

The etch-primer bores its way into the oxide-film and provides a 'key' for the paint to stick to.

ok but does it matter if I put a full coat on all panels rather than just a dusting? - I'd prefer full coat so that I can see any dents etc I have missed and then rub it back......like you would with normal primer.

any issues with that?

[Team Idris]

Might crack? And too much acid.

I hear what you are saying. Proper job would be spray cheap gloss right on the panels to see the finish. Then strip that off when its right and begin etching. Long winded, but, seeing how I get caught out between primer and gloss for things like swage lines, you should finish up with a better job overall

[jameshub]

Might crack? And too much acid.

I hear what you are saying. Proper job would be spray cheap gloss right on the panels to see the finish. Then strip that off when its right and begin etching. Long winded, but, seeing how I get caught out between primer and gloss for things like swage lines, you should finish up with a better job overall

do you mean the etch primer might crack or the top coat might crack? - problem I have is that I don't have anywhere to do the actual spraying for about 6 months so I was basically going to roller the etch primer all over (not thick but one coat) then let it harden and rub it back, then use the vehicle as is until I can spray top coat.

I guess if its going to crack, it will do it soon?

[Les Brock]

You could always use this....

http://www.amazon.com/U-POL-ACID-PRIMER-M-I-R-COMPLIANT/dp/B003ZWDZ9I

[Boris113]

I found 3 rattle cans of Halfords etch primer was more than enough to give the whole land rover a dusting, inside and out.

For that price, it wasn't worth buying a tin of the stuff and getting the spray gun out.

I didn't do mine in quite such detail as has been described, but a light dusting of etch, leave to dry for at least 12 hours in the garage then started spraying the nato green. In hindsight, a high build primer may have been a good idea, but it's come up well for my first attempt with a spray gun.