Preventing corrosion

[notsofast]

What's the best way of preventing corrosion (thinking mostly about underbody areas and engine bay)?  About 3 years ago I got a garage to do a Waxoyl treatment, though I don't know how good it is (and not sure if it was applied thoroughly).  When changing the exhaust tailpipe yesterday I noticed the rear axle was quite rust-covered (though still solid), and there was a bit of flakiness around the weld/join between the floorpan and the rear panelwork.  I smeared a bit of grease over affected areas but then wondered if this was a bad idea (i.e. would it do any good, and would it be incompatible with the Waxoyl)?

[Kieron G]

On seams under the car I've brushed on waxoyl but the cavity soft type not the underseal. Found in past that rust can continue with the underseal. I guess it will wash off over a long period in some places though. The flat areas behind the headlights that seem to like to rust I mixed the waxoyl with a bit of old gear oil I had and brushed it on also the area under the plastic scuttle below the windscreen which can rust through from the inside.

[oilyrag]

The 'soft' Waxoyl is good and relatively easy to apply with a brush - spraying it can get very messy. It can also be over-coated in the future. Make sure any sizeable flakes of rust are scraped off before treating. The rusty axle, apart from where fittings are attached (to make any future removal easier) , isn't going to rust away, so not really worth coating.
Grease isn't very good at all as it can absorb water (it's a bit like a soap).

[notsofast]

also the area under the plastic scuttle below the windscreen which can rust through from the inside.

Ah, could this be the reason why on my M49 the back of the engine bay (and also inside the front wheel arches) gets damp when it rains?

[notsofast]

Grease isn't very good at all as it can absorb water (it's a bit like a soap).

I didn't know that. Good job I didn't smear it everywhere. Though I did put it around the engine bay last year (water was getting in), so I might re-do with the soft waxoyl.

[Kieron G]

also the area under the plastic scuttle below the windscreen which can rust through from the inside.

Ah, could this be the reason why on my M49 the back of the engine bay (and also inside the front wheel arches) gets damp when it rains?

I think so but might be normal. I can't remember where the pipes which channel the rain water out of the gulley under the windscreen are routed. It is worth clearing any dead leaves etc out of there. Would be a case of removing wipers and the two parts of the plastic trim under the screen held on with quarter turn screws

[notsofast]

When people say to use the 'soft' Waxoyl, does that mean the 'original' formula, as per this: https://www.halfords.com/motoring/paints...91916.html.  I had popped into Halfords but wasn't sure which version to buy (they also sold the underbody sealer and another form that I can't remember, but only the original sounded like it might be 'soft').

[oilyrag]

Yes, that's the stuff - the underseal type is usually in a tin with a big lid. You can thin it down with White Spirit. Keep it in the warm and after a really good shake it will pour into something like a jar allowing you to use a paintbrush. Once thinned I have used a sprayer to apply it but it forms an aerosol and blows about and a lot ends up as a mist over the floor, you and things you forgot to mask off.

[notsofast]

Thanks. Yes I saw they also had some sold in a sprayer.  I guess spraying would be a good method for areas that are awkward or inaccessible with a brush.

[boop]

I soak all door and hatch cavities in Motip hollow section wax yearly. Rust will not be surprising me from inside out.