Classic cars forum & vehicle restoration.

[Greeney in France]

I am at the stage where I could start to strip to bare metal the main body tub but then I would apply an etch primer just to protect it from rusting over while I do other things but is it best to apply filler on to bare metal or is etch primer OK?
Obviously I could etch primer it all then just DA off around the area to be filled if necessary.
Is etch/wash primer porous? I understand primer filler is so its best to top coat it quickly after is this right?
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[Phil - Nottingham]

The etch primers I have used must be overcoated quickly - there may be others that will wait a while Filler is best applied to bare metal where possible although not essential
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Rover P2
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Rover P5 & P5B
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[Gaz]

Filler is best applied to bare metal, although most newer products can be applied over sanded paint. This also depends on wether you intend to repaint your vehicle with Two Pack paint of the old Cellulose.

Self Etch/Wash primer is porous and should be overcoated with a high build primer very shortly after the etch is applied.

Your best bet in my opinion, is to use a two pack primer, following all the health and safety instructions of course, as your health is most important, as the two pack primer has good etching properties which isn't porous, it aslo has the benifit of being an excellent hiugh build primer, and as you say, could be sanded off to facilitate a repair if you wanted to at a later date.

[thamesdfo]

My preference is to apply epoxy primer over all bare metal, to prevent flash rusting. (not sure what the "HOT" brands are in Europe and the UK, but in N.A., PPG/Ditzler's "DP" series is widely used.
These days, I believe you will find that many are using an epoxy primer UNDER filler. (of course, the primer must be scratched up first to give the filler a means of mechanical adhesion). The logic being that epoxy will protect the bare metal from moisture, whereas filler applied over bare metal will readily absorb moisture, which will subsequently cause rust on the bare metal.

HTH
James

[magic9r]

General bodyshop rules are to apply filler to bare metal, it's not the type of paint that maked the difference it's baking in the oven, filler over paint has inherent risks of air pockets breaking adhesion to the paint & bubbling.
If you want to protect bare metal just ensure the area is well ventilated and you can safely brush paint 2K primer (lesss thinner than for spraying) activated with a winter hardener. This gives you excellent adhesion and a fully waterproof, easily worked coating, it's also handy for temporary protection of part finished repairs as it seals filler preventing water absorbtion. You can drive a car with filler or metal porotected in this way on UK winter roads without compromising the final repair,
Regards,
Nick