It’s just starting to become visible inside the rear arches and has spread in places to about 15mm back from the lip.
I have a big tin of Hammerite but I’m not sold on this stuff, I used it around the numberplate light holes in the bootlid last year and the rust has started to reappear.
Here’s the plan:
Careful use of a wire wheel to remove all the rust and feather the edge of the good paint inside the arch lip (so nothing will be visible on the outside of the car).
2 coats of Rustbuster 121 mastic epoxy in silver directly onto the wire brushed metal.
If the colour difference doesn't look too bad then leave it at that.
If there's a start difference in colour then a light sanding inside the arch and mask and spray with a rattlecan.
Sounds like a plan. Certainly better than leaving it. If you take it to a body shop it will come out looking as good as new… maybe even for a couple of months. You will probably treat the problem better than they will. If it hasn’t gone as far as the outer edge then now is the time and the right weather for doing it.
Unfortunately rust can’t be cured,it is in the metal best to leave it save up and have it cut out,sprayed at a body shop.Seems that Mazda is the only modern car that rusts nowadays.
Thanks for your response Roadie, I’ve heard many reports about garages doing the arches only to reappear a short time later. Hopefully I can keep it at bay for a few years an then look at it again.
It is very hard to clean up pitted metal and/or blobby welding, so the problem often comes back very quickly. Get recent recommendations and, if possible, a guarantee of 5 years. It is possible to restore cars properly but few places seem to manage it.
I did this last year on my arches. Ground down rust and painted with Finnigans No 1 then body colour. So far no reappearance of rust. However I used a magnifying hand mirror to check that I had fully removed the rust. I also removed the rear arch covers and jet washed underneath. a lot of mud gets caught in that arch. Everytime I wash the car I use a J cloth to clean the rear arches which I then throw away.
Yes apparently you can’t paint over it, but mastic epoxy is fine to paint over.
Rustbusters recommend marine striping which is painting along the bare edge first, I’ve also read that rounding off the square edge helps the paint to adhere. This is where the rust started so I’ll be doing everything possible to keep it from coming back .
Water gets in between the inner and outer arches (the joint has some kind of factory sealant in between then at the lip, but it fails eventually) and nothing you can do on the surface will touch it. From looking under the car, I suspect water can also get in via lightening holes in the “chassis rails” where they kick up over the wheel arch and runs down into the sill area just in front of the wheel, which doesn’t drain properly.
Pop off the mini wheel arch liner, remove the rubber bung in the front of the arch and peer inside with a torch. Often one side is clean and the other has rust in the bottom of the cavity where water has been sitting. Mine never needed touching on the nearside and was just shiny steel inside but the offside rusted, was welded with repair panels*, then rusted again.
*by a garage recommended in STHT - but their super-conscientious welder left in the six months between the article being published and the job on my car, which was bodged by someone else
really? there are some shocking cars out there still, not least of all some Mercedes, and only read today in some circles the VW Golf has a bad reputation for rust in the arches.
According to an article in Auto Express a couple of years ago, rust is on the way back in modern cars, as body panels get lighter and box sections get more complicated. And there was even a league table of rotters, gleaned from MoT results, I think.
Thanks for your suggestion but I’m dubious about using a rust converter. I used kurust on the boot which is also.a rust converter but the rust has begun to come back.
How do you know it’s converted all the rust?
How much do.you apply?
My application changed colour and I’d previously rubbed it down but the rust returned.
Just a bit wary of these products and leaning towards complete rust removal.
Got the car up on stands, removed the arch liners and cleaned away the waxoyl directly behind the arch returns (this took ages to completely degrease)
Used degreaser and salt remover before getting in there with the wire wheel
Practised on an old freezer first to get to grips with the wire wheel (horrible nasty thing but very effective at cutting out metal)
Removed all visible rust from arches back to bright metal
Rounded of the edges on both arches and feathered back the paint
degreaser and salt remover again
1 thick coat of (by brush) of unthinned mastic epoxy striping along the edge, then inside the arch return and then on the outside to within 10mm of the edge of the flared wheel arch.
left overnight then another coat of slightly thinned mastic epoxy
She’s still up on stands curing and on Thursday I’ll be spraying waxoyl back on the inside of the arches and refitting the archliners. According to the datasheet at 23c the mastic epoxy needs 10 days to cure before putting any oil on it but I need the car, so 5 days in this current warm weather will have to do.
As a side note this past winter and the unrelenting salt spreading of our roads has really taken it’s toll on her underside . I had a full underseal and cavity wax done last spring but even so there is light rust all over the bottom of the chassis and some components.
This epoxy mastic stuff is really good stuff, dries really hard and has bit of give too, if this was a project car and not my everyday drive I’d be inclined to remove underside components, wirebrush then paint with mastic epoxy and refit. I might even get back under there another time this summer with a wire brush and paint on as much as I can before winter.
. I had a full underseal and cavity wax done last spring but even so there is light rust all over the bottom of the chassis and some components.