paint reaction

[Tractor Boy]

Hi

Just getting ready to repaint my defender. Bonnet rubbed down and painted in the new colour - all good.

Body is pretty much repaired and prepped with one small problem.

In a couple of areas of ended up rubbing down to bare ally.

Sprayed etch prime onto these areas and getting a reaction to the etch prime.

Whats the fix?

Thanks in anticipation. Need to get her painted and put back together.

Ian

[western]

different typres of paint will react with each other, a sealer or barrier coat of clear might be required prior to your chosen paint type & colour.

[Tractor Boy]

thanks for the quick answer. Will see if i can pick up a rattle can of clearcoat tomorrow.

[Scotts90]

Exactly what is reacting? The etch on the aluminium or the top coat on the etch? If your etch primer is straying into areas with paint then this may react as the etch is trying to eat into the substrate to bond.

[Eightpot]

Presume the etch is reacting with old paint surrounding the bare aly?

The old paint could be made using a base that reacts with the chemicals in the etch, and you're probably applying etch too heavily.

I would suggest sanding it back off till all trace of reaction is gone, wipe area with degreaser/panel wipe and then reapplying the etch primer but only with a light dusting. Don't spray it on like you would a colour coat, it's just to provide a light key into the metal. Apply primer or colour coat not long after etch has dried.

[Tractor Boy]

eightpot is right, the etch is reacting where it's coming into contact with old topcoat.

Will try sanding back and taking it easy next time around.

Not painted a car before so this is all new. Want to make a half decent job of it.

Thanks to all for answering.

[Souster]

Is the etch reacting or is it a silicon reaction?

[GW8IZR]

are you putting the etch coat on too thick on the first pass?

try a dust coat and then go back over it ten mins later see what happens

[Team Idris]

Yeh, but if you 'dust' an etch it won't etch because there won't be enough active acid to cut through the oxide ( I was told by the supplier of the two pack aircraft grade etch primer) .

[GW8IZR]

Yeh, but if you 'dust' an etch it won't etch because there won't be enough active acid to cut through the oxide ( I was told by the supplier of the two pack aircraft grade etch primer) .

A good coat of etch is better but we arent dealing with new bare metal, there needs to be some compromise here - and using a sealer or stabiliser stuffs the etch anyway.

if you take all the old paint off completely the problem will (probably) go away, sticking anything on to stop the reaction will be counter productive.

[Souster]

I personally think an etch primer should be dusted, I've always been informed that by body shops and paint specialists. A thick coat isn't necessary for an etch primer.

[GW8IZR]

caused me to dig out the paperwork for some 2k I have here :

it suggests dust coat and over coat if you need high build, anyway YMMV :-)

I have some brush on etch which I was given years ago and I've never seen anything stick like it. I have no idea what it is apart from the fact its blue! but I'll be sad when it runs out and it only gets used on MY projects.

[Tractor Boy]

Just wanted to update and to say thanks to all who answered.

Gone back to it tonight and it looks like a lighter coat has done the trick, thanks all.

Hoping for some decent weather this weekend to get the topcoat on. Fingers crossed.

[GW8IZR]

'er brother who paints for a living always complains I put too much paint on :-)

he is from farming stock and I swear he counts every pass of the gun as a loss of profit .......