Help a newbie decide best rust prevention?

Ok so the jimny that I am hoping to buy next week wants a good clean underneath as it's a little dirty and has a bit of surface rust, I want to try and treat the jimny as best I can and have seen an item on eBay called Hammerite Underbody seal with added waxoyl I've been reading a lot about the rust protection and hear a lot about various methods but this one sounded ok to try out?

My question being totally new to all this type of stuff is what the hell do I do with it?! Haha. Do I have to rub the whole underside of the car down first with a wire brush/ treat with a rust beater paint first or just apply the hammerite straight to the underside? Can this hammerite stuff also be used internally like in the jack part of the boot where there is the odd sign of the start of rust patches?!

As I say I'm new to this and being a typical girl no nothing about removing panels or parts of the car so I would literally be hoping to paint the areas I can reach including in the front of the engine near the front lights? Can this be applied on the exhaust and all the axle/ ball joint areas? Sorry for all the questions I'm just majorly confused by it all!

For surface rust inside the car rub the rust down apply a rust treatment paint then paint with normal hammerite.

Not to sure about the hammerite with waxoyl, does it dry hard as some underseal seems to stay wet/tacky forever.

On mine I rubbed the axels radius arms steering rods panhard rods etc down and painted it all with hammerite, mine wasnt to rusty tho.

think most people rub down rust treat then re paint the bits in the engine bay, if painting the engine block itself you need to use high temperature paint.

Not sure about underneath, should imagin you clean as well as you can rub the rust down then liberaly apply undrseal/waxoyl or wwhatever you decide to use.

What you have to do is remove all the rust first. This is pretty much impossible under a car.

So you need to apply something that sticks to rust and converts it to something else (not sure chemically how this can work)

I have tried in the past

Jenolite (phoshphoric acid) - doesn't work
Rust -eater- doesn't work

That loctite stuff that is purple - doesn't work

Waxoil - doesn't work
Dinitrol - doesn't work : bit of a pattern developing here

The recommended stuff is POR-15: like hammerite you remove loose rust and daub it on.

You can then spray the dinitrol over the top if you like.

I have sprayed inside my chassis and sills with dinitrol, if it works a little bit I suppose it can't hurt.


I have painted underseal with waxoil over the top of the dinitrol stone chip under my wheel arches, and it isn't long before rust marks appear (then I daub more underseal over them

In The Olden Days I used to continually spray old engine oil inside the sills and all over the underside of the cars, and they still rusted like mad.

What you really need is the stuff they paint oil-rigs with in the North Sea, someone once told me it is made by Ameron, and is over £100 a litre.


In summary:

remove loose rust and daub with POR-15, hammerite, or that metal paint that lidl sell @ £10 a litre.
Spray dinitrol into the sills and cavities.
Waxoil underseal over this if you must.

Don't let it get muddy and stand with damp mud stuck anywhere, wash it underneath 10x as often as you wash the top, and then take it for a drive on dry roads to dry it off underneath.

Bloody hell there's a lot of processes to it then that stuff on eBay says to just paint straight on and then you don't have to add anything else to it. So do I paint the exhaust too as around bear the wheel bearings?

wait until it is hot & sunny (2021 probably)

Pressurewash the underneath, this will remove most of the scale, flaky underseal & rust.

Wait a few days for it to dry properly, drive it around to make sure that the water has a good chance to run out of any nooks & crannies.

Then POR-15 anywhere that has rust or bare metal.

You can paint the exhaust at the back, paint the tailpipe and the elbow that comes out of the silencer. It will smell as the paint burns off a bit though.

Then if you want, you can stonechip or waxoil underseal the whole of the underside when the POR-15 has dried.

Not sure what you mean about painting bearings: by all means paint bearing housings and the axle cases, paint won't stick to bearings as they are covered in grease.


Most of the rusting happens where Suzuki cleverly put double skinned panels, like under the rear seats, and jack compartment, although you can get pretty much anything to rust by covering it in wet clingy mud and leaving it.

As above, warm weather I did exactly the same.
Painted metal parts with Hamerite then waxoiled everything I could reach on a set of ramps.