Checked my fabia's sills and there is rust creeping under the paint. I had odd rusty bit that turned out to be stone chip and not deep rust. I discovered thearea just ahead of the rear wheel is susceptible to corrosion.

There is a fibre/plastic - tar manufacturer rust protection under paint. I used sharpened wood chisel to remove. The metal flaked. A hole has appeared. The rust has progressed under the sill rather than from above from wheel arch.

I've previously used etch primer elsewhere, high build, topcoat, clear coat. Not always that durable.

I bought stone guard spray paint to protect against stone chips which is why I was prepping sills.

I've rubbed rust down to bare metal except some rust in pits of metal. I was going to use rust converter but read it is not compatible with primer.

I'm going to use epoxy p40 isopon and some P38 after curing. I'm using epoxy spray primer 2k. I read I can add putty isopon first then the epoxy primer after curing or vice versa, as long as properly cured.

The reason I'm looking at epoxy is that it is fully waterproof and stops rust.

Can I add stone guard over epoxy primer then top coat 1k then 1k or 2k clearcoat?

If not how would you do it?

Is this correct?

Thanks

Front is not too bad, just behind wing - see image.

Both sides of car rear end of sill are affected. The paint there looked fine and no bubbling.

Since photo taken I've rubbed down rust.

Edited 16 August16 Aug by bmbmdmb

My octavia is the same but weird my sons 55 plate fabia is spotless. Think it depends on what part of the country they have been in due to road salt. Have a look at Bilt Hamber rust cure. Seems to work well and can be overpainted and also a reasonable price. Hydrate 80 is what I use. £25 per 500ml

Alasdair

My red one was doing this, perhaps not quite as badly but in winter I try to pressure wash in the arches fairly often. I sanded it back with a dremel, applied copious amounts of rust converter, primer, then rattle canned it with alleged Flamenco Red (which most of the car still is). Was a place in Co. Tyrone (I think) that sold me the paints and they're a bloody good match.

On 18/08/2026 at 17:10, Alasdair1 said:

My octavia is the same but weird my sons 55 plate fabia is spotless. Think it depends on what part of the country they have been in due to road salt. Have a look at Bilt Hamber rust cure. Seems to work well and can be overpainted and also a reasonable price. Hydrate 80 is what I use. £25 per 500ml

Alasdair

It is regularly washed. I've had rear bumper off 2 years ago to rust proof hidden areas and wheel arches have been off numerous times. No rust.

This rust was hidden under the factory paint and stone chip protection. As the sill protection is bubbly in appearance there was no tell tale signs. Discovered entirely accidentally when prepping sill.

I bought a couple of Bolt Hamber products recently - Underbody and the clear stuff. 80 hydrate for chassis voids.

On 18/08/2026 at 19:54, AnnoyingPentium said:

My red one was doing this, perhaps not quite as badly but in winter I try to pressure wash in the arches fairly often. I sanded it back with a dremel, applied copious amounts of rust converter, primer, then rattle canned it with alleged Flamenco Red (which most of the car still is). Was a place in Co. Tyrone (I think) that sold me the paints and they're a bloody good match.

I've read that primer over rust converted rust is a bad idea, unstable surface , but probably better than not doing anything.

Hycote diamond silver is a good match but the power red 50b for my astra was nota match. I went to paint shop. The base primer is coloured and gives depth to colour.

I've got epoxy primer and going to seal it tomorrow.

Should I rub down rest of sill to metal, I'm thinking not because the rust I found is creeping from direction of wheels towards centre of sill. I've found not rusted metal a little further in. Probably best not to disturb

Edited 19 August19 Aug by bmbmdmb

Problem with the stone chip guard it gets brittle and cracks with age then moisture gets trapped underneath. If the rest is solid I would leave it alone.

Alasdair

12 hours ago, bmbmdmb said:

I've read that primer over rust converted rust is a bad idea, unstable surface , but probably better than not doing anything.

Yeah it was just to seal it more than anything else. It seems to have done alright, I do it every 2 years or so in various places. It's still very solid though - and ready for me to get it sold now.

The red one has been in Scotland since new, and that's not a good climate.

When I did this on my old Nova I just used silver Hammerite... It lasted well

I had to have a hole welded a couple of years back. Rear of sill is close to mounting of rear beam.

This (actually part of front wing) has been slowly worsening for a while. Went through MOT a few weeks back without mention. 🙂

I spent a few days on this and did brakes (clean and lube and paint) and also under wheel arches. P40 isopon worked a treat.

I only started this to sort a few rust spots due to stone chips which were superficial. Digging around lead to the discovery of rust. When you see bubbling it is too late.

The cavity was sound. I've sprayed s50 bolt hamber wax and used the clear wax stuff under wheel arches.

The photos show the epoxy spray 2k after chiselling off old paint and then sanding to leave the factory rust proofing, the paint was lose after a sandpaper rub down.

Had stone guard grey and then hycote topcoat diamond silver then clear coat.

No adverse reactions. The stone guard spray I didn't rate, seems consistency of a primer.

The underbody bungs I replaced with aftermarket. There are several sizes 30mm hole along sill x4 each side, but some near exhaust etc. iñ wheel arch the hole is 40mm, see new bungs in photo.

Edited 54 minutes ago54 min by bmbmdmb