Advice needed on tackling rust under sills

I need to remove rust from under the sills, including rusted seams, and to re- coat them in the best way to protect them against future chips and rust. The rust problem is not serious at this stage - it is only on the surface - but a stitch in time saves nine! I am not too bothered about the cosmetics - after all, I don?t intend to spend many hours on my back admiring the underside of my car!

The existing paint is lacquer-coated metallic finish. There are quite a few areas which I repaired last year with standard primer and metallic paint, but this has not lasted well. Also, some seams underneath the car are starting to rust badly. What I now intend to do is:

(i) Wire-brush all rusted areas down to bare metal.

(ii) Treat the exposed areas with a product that makes the rust remaining in pitted areas inert.

(iii) Treat the rusted seams with a similar product to attack the rust within the seams and seal them.

(iv) Paint over the whole area under the sills (including the areas still covered with paint + lacquer.) with some form of chip-resistant paint or underseal.

It is years since I?ve tackled anything like this, and I am not up-to-date regarding materials. I would welcome any advice as to whether my general approach makes sense, and specifically:

1) What is the best product to render the remaining rust on the exposed areas inert?

2) What is the best product to apply to the rusted seams?

3) What product(s) should I then apply to the treated exposed surfaces and the surfaces on which there is still paint + lacquer?

4) How should I treat the surfaces covered by paint + lacquer prior to applying those products?

Many thanks.

Reply to
Ubtree
Loading thread data ...

To be honest if this is just a daily runbabout and looks dont matter i'd just wire brush all the loose crud and rust off and then apply waxoyl or dinitrol, i tend to find the oily wax type products much better than underseal as they dont crack and flake and there is less chance of water getting underneath.

A good coating of wax topped up every year ought to keep the tin worm at bay for a good few years. The trouble with repainting is its almost imposible to get rid of the old rust and it just starts again hidden under the new paint until a friendly MOT tester sticks his screwdriver through the rotted part!

Dilbert

Reply to
Dilbert

I do much the same. I use the underseal/waxoyl stuff in the black tins. Brush it on for areas I can get to and use a the spray can version for difficult to reach places. It stays flexible and oily for months. Old engine oil is good to squirt into box sections. I use one of those old oil cans with a trigger and long flexible nozzle. If you don't mind spending bit more then use waxoyl instead of old engine oil. A bloke told me he used to melt half a dozen candles into old engine oil and said it does the same job as the £25 quid tins of waxoyl. Could be an urban myth, but sounds plausable.

Red oxide and paint is ok on new metal, but not much cop where rust is concerend.

bucket

Reply to
bucket

Waxoyl is pretty naff when you see it tested against Dinitrol etc. I'd not use it on metal alone, at least etch it (VW seem to dip prime and wax everything).

Reply to
Doki

Thank you very much for the responses, Dilbert, bucket and Doki. I can see that I was going to go about things the wrong way. I have done some research on Dinitrol, but this has given rise to some more questions, and I was hoping that you could help with these.

  1. Would you apply the Dinitrol over the entire area - bare metal and painted metal?

  1. How is the coating maintained? You mentioned ?topping up? every year. Is this just a case of recoating areas where the coating has cracked or worn away, or from time to time do you need to remove the lot and re-apply?

  2. Are there any special products to apply to seams where there are signs of rust, to penetrate the seams, cure the rust and seal the seams?

  1. I have read about treating the box sections by drilling into them and spraying, but have never previously dared to do so. Is this a relatively straightforward job, or one best left to the experts?

Reply to
Ubtree

Rust is like a cancer and once it takes hold the only real option is to cut it out. I've generally found rust converting products to be a waste of time.

One of the best rust-prevention methods is to have an engine or gearbox that leaks oil :-) So if you regularly spray old engine oil into the crevices etc that should do the job. You want to stop the rust spreading as much as convert the current rust. I've found waxoyl underseal to be good but the waxoyl oil spray stuff isn't easy to apply.

There should be drain channels in the sill that you can use to spray in the oil so you shouldn't need to drill any holes.

Reply to
adder1969

Yeah, agree it certainly is not easy to apply even on a hot day when its a bit more runny. Still got a full 5 litre tin of unused waxoyl in garage for that reason. As I try to avoid working on car or van as much as possible the waxoyl/underseal spray can is handy for a quick bit of protection to get an old banger through the winter in good shape.

There are lots of drain holes in the box sections. Block them before pumping in oil/waxoyl so it doesn't run straight out, but remove blockages after a few days and make sure the holes are nice and clear after so water can drain out and a bit of air gets through.

BTW Goggles while brushing off that old rust. Its horrible getting the grit in your eyes.

bucket

Reply to
bucket

I now use phosporic acid in lovely liquid form from agri suppliers. It's Jenolite without the jelly or hideous cost, so can be put in a garden mister type spray bottle and applied very easily. Just don't inhale the fumes!

Reply to
Stuffed

Rustins do a similar product in a 250ml bottle for about £2 from your local hardware shop...

I have used it in small areas before blasting with hammerite if it isnt somewhere that is seen.

Tom

Reply to
Tom Burton

I remember seeing a guy on TV using citric acid. It may get rid of the rust but of course it won't stop the metal from continuing to rust.

Reply to
adder1969

1 gallon for under a tenner :)
Reply to
Stuffed

MotorsForum website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.