Rust, filler and primer.

[The Griffalo]

My Volvo has a small patch of rust near the sunroof seal. Rather than wait for it to go right through I've just sanded it and stabilised it with rustproofer. As the original paint is fairly thick I need to apply a thin coat of stopper before I paint it. So do I apply the stopper before the zinc primer or after?

[Anatol]

The zinc primer works because zinc has a higher affinity for oxygen than the steel in the car body. Should any corrosion occur, the zinc will take the available oxygen and corrode, it's essentially sacrificial.

That means it should be next to the steel.

The stopper will need a decent key to bite into, or it will delaminate from the surface it's on.

Zinc primer is usually not intended to be sanded once sprayed.

This leaves you with a bit of a conundrum. You'll either have to put several coats of zinc on, enough to be able to key up with 400, or whatever your stopper needs, so that the stopper will bite to the primer layer, OR you could try using a high-build sprayable primer/filler that is compatible with the zinc to add the build you need, rather than stopper paste, as this may need less of a keyscratch.

Either method should work.

HTH

Tol

[The Griffalo]

Thanks for that, I think the high build filler/primer is what I need as I'm not really filling, just building up thin aerosol based paint to the manufacturers original depth. It's only a £600 Volvo so it's not really worth taking to my local Chips Away guy

[dxg]

Have I missed something, then?

Being completely new to this sort of thing I went for

grind back to bare metal > multiple layers of zine primer > then high build primer

and that was pretty much it, this was a couple of months ago and now sign of anything returning. Stil waiting for enough time to mess about with final colour...

Is "stopper" something specific?

I'm sure other novices like me would be reading this and would appreciate advice or direction...

Cheers in advance!

[The Griffalo]

Stopper is just a very fine filler. How did you get on with the filler/primer?

Personally I tend to use a rust stabiliser first just to kill off any reaction that's going on.

[Anatol]

The Griffalo said:

It's only a £600 Volvo so it's not really worth taking to my local Chips Away guy

Well, if you want to make a day out of it, feel free to pm me - you're more than welcome to bring the car and your supplies to the workshop and do the DIY repair here, with unlimited tea/coffee and natter, and access to useful things like IR lamps.

See, PH memberhship benefits all over the place

Tol