Rust Proofing best practise??

[wmitchell]

Hi all,

Found a (very) cheap vw polo for sale near me with plenty MOT left that I'm tempted to pull the trigger on as it needs a few minor bits doing to it and thought it may be an ideal means of entertainment (frustration) while in lockdown. Previous MOT advisories suggested it had some surface corrosion on the front subframe, thought it may be worth getting at it with some rust treatment to prevent any catastrophic rot.
Done a little bit of research on how other people have tackled this, my assumption was that most people sanded/ground off the surface rust, then applied some kind of polymer-based coating like Waxoyl to the surface. I've since seen a few YT vids which suggest using 'rust converter' to prime the surface of the frame, and then some kind of thick paint that will resist stone chips/salt etc.

The Waxoyl route seems cheaper however, I've heard stories of metal components continuing to rust underneath the sealant as it's managed to trap moisture underneath, whereas using rust converter and paint doesn't seem to cause the same problem as it seems to adhere better to the metal. Was just wondering if anyone would recommend using one over the other?

Thanks

[GreenV8S]

Waxoil is not an alternative to paint, it is a way to help the paint last longer by sealing any small cracks or chips that develop.

Paint or paint and waxoil will slow down corrosion but not reverse it, so if you have any existing corrosion problems you'll need to repair those before you do anything else.

[LennyM1984]

You just need to seal the metal from the atmosphere. If you can do this you will prevent the rust from developing further. It isn't an organic thing and so won't "grow" beneath paint/waxoyl... if you can get a decent seal.

The issue is that it is typically very hard to get a decent seal (very few paints will stick to rust as it is flakey/powdery and waxoyl can crack/dry out) and/or that the rust is coming from behind and so painting/waxoyling the top is not really sealing the problem area. In both of these cases, the metal remains exposed to the atmosphere and so the oxidisation process can continue.

If it were me, I'd clean it up as best I could and then spray it with several coats of Comma Waxseal. I've found this to be surprisingly good at coating metal/rust and it creeps into every nook and cranny. I accidentally got some on some paintwork and it was a nightmare to remove (repeated use of panel wipe, alcohol, claybars etc)

[Chris32345]

Flap disc and grinder get as much back to bare metal as possible
Degreaser then rust converter
Couple of coats of spray on primer then top coat e.g stonechip hammerite
And possible waxoil or other type stuff for final layer

[paintman]

Was advised many years ago by an MOT tester that a 50/50 mix of clean engine oil & grease applied with a brush was the way to go.
Environmentally friendly? Definitely not.
Effective? Very much so.

For those that are familiar with older rwd cars the area around the rear of the gearbox was often caked in a mix of dirt & gearoil built up over the years. Scrape that off & the paint & bodywork under it would be pristine.