Effective rust treatment?

Get rid of it. That's the only way to "treat" rust. Get rid of all of the rust, and then paint it again. I've painted a wing that I treated with Bilt Hambers "De-ox" stuff, and it can't get rust out of pits, and it's already looking like it'll bubble again. Would have been a hell of a lot quicker to go and buy a decent scrap yard wing, and if you value your time at all, a lot cheaper. Take the panel back to bare metal with a 40 or 80 grit disk on a DA in grinder mode, make sure all the rust is gone, and then prime and paint it.

If it's pitted, IMO you might as well forget about it and go looking for a new panel. You'd even be better cutting the rust out and bodging it with filler.

Jenolite's pretty good.... or POR15 'paint over rust' is supposed to stop rust dead in it's tracks. It's a tough epoxy based paint...

Of course the only sure way is to cut out all rusty metal. rust bubbles usually start inside out so are tricky to repair....

The only way I have found that works indefinitely on genuine surface rust, is to sand blast the surface, then use zinc primer. A spot blast gun and media is about twenty quid, even a little compressor will do for small areas.

Mrcheerful

That's because you're not actually removing all the rust.

I've mainly used phosphorous pentoxide based

Sanding, scraping, wire brushing are all very well but they won't remove every bit of rust right down into the pits it forms in the metal. As long as some of those remain they'll grow back again. The only way to treat rust fully is remove it fully. Aggressive media blasting or cutting out the affected areas is the only way to really remove rust. 'Rust converters' will change the top layer into something inert but not stop the rot underneath growing back. Once you've really removed the rust back to bright metal then any normal primer and paint will give you a normal rust free lifespan again. Half measures will achieve exactly that - more rust in half the time sometime later.

As said, sandblasting down to bare metal is by far the best. Failing that, I use a stiff wire brush on a small angle grinder to get as much off as I can, then use Jenolite (or a phosphoric acid based fluid) with wire wool to rub it in. This usually removes pretty well all the rust. Then a decent primer etc.

If it really was surface rust, then a combination of wire brushing before and during treatment should work well enough - the idea is the acid has to penetrate *all* the rust to neutralise it. Leaving the odd lump here and there simply won't work - and often what looks like surface rust has penetrated anyway. The pother thing is how you're making good the result - plenty of body fillers are porous and rubbing down wet just introduces water and starts the rust all over again.

Non. To treat it successfully you need to grind it back to good metal or cut it out.

Absolutely spot on! Exactly what I'd recommend, sand blasting is the only way to get rid of rust when its in pitted metal, rubbing with sanders or grinders just treats the surface and doesn't get into the deep ingrained rust.

Stephen.

It also tends to blow holes (or enlarge existing pin ones) where the metal is thin leaving no doubt as to the condition.

Thanks all. Good useful stuff. Makes sense.