Help with the dreaded RUST !!!!!

[WELSHVIKING]

Hi,
I have decided not to replace the front door of my xantia estate, i am just going to treat the rust at the bottom of the door. What i need is advice on any good rust repelent what you kind people may have used. I realise there are lots of makes of rust repelent but i need one which is hopefully going to keep the rust away for hopefully as long as i own the car. The car is the usual dark green colour so any advice on primers, rust repelents etc etc would be appreciated...Thanks

[dnsey]

AFAIK, the only reliable way to treat rust is to grind / sand it all away on both sides of the panel, then waxoil or similar the inside after finishing. Perhaps it's just me, but chemical rust treatments never seem to last very long.

[Peter.N.]

The best treatment for the insides of doors, once you have repaired them, is to pour engine oil into them once a year. It makes a bit of a mess as it runs out of the drain holes but once you have wiped it over a few times it will dry. The same goes for any other hollow sections.

Waxoil is very good at rustproofing flat areas especially if you apply it in hot weather but it doesnt creep into the seams like oil does. Dont use used engine oil, it makes a terible mess!

[bxbodger]

If you want to stop the rust advancing, there's only one way- cut it out and weld in new steel- believe me, its the only way.

It doesn't matter what you treat it with, the rust monster NEVER sleeps and it will be back through in a couple of months.

I know - I've got a Triumph !!!!!

[fridgedoc]

Hi all

I don't want to poke my nose in here but I will .............

why not just change the door, a decent 2nd hand one would not be that expensive, if it helps I am going to a breakers tomorrow who has a "L" reg sx very clean, I'm getting a few bits for myself, I will ask him what he wants for a door, it is admiral blue but you would need to spray whatever way you go.

RUST never sleeps !!!!!

[AndersDK]

It is in fact possible to get rid of rust for good - the chemical way.

Those ready made rust eaters you can buy are made the same way - but the solutions are very weak not to harm anyone.
The secret is to use a weak Phosphor acid to deep clean the rust and then a solution containing Zinc in the chemical form of Zinc powder. The Zinc powder wil instantly neutralise the acid and form a thin chemical layer of Zinc - galvanisation. The remainings would always be the Zinc powder as the acid is totally neutralised.

I found this description on a site for a diving-club where they had problems with rusty Oxygen flsaks. They used the above method to galvanise the flasks internally.

I'm sure some of our members have the deeper chemical insight in whats going on in this process - and how to find common trade products hat can be used in the process by DIY 'ers ?

[fridgedoc]

Hi Anders

Well Anders, I can't argue the point as I do not know whether your idea works or not, although I do understand what you are saying and it may well work, I've only had experience of the diy kit and that was many years ago and it did not last too long, I guess to be on the safe side the diy product is very weak, must say you have made a very interesting point, I might just try it out on a rusty piece of metal. mmmmmmmm

[jeremy]

How to prepare depends on what's going on. If your door is simply scrufy as the paint has fallen off, leaving rusty but unperforated metal then cleaning off really thoroughly and thoroughly painting will work. A good primer would be a good idea - phosphoric acid based products will neutralise rust and are also a good base for adhesion. Zinc can be useful but to be honest a good coat of commercial primer filler as used in bodyshops will do a good job if it is appleid quite thickly and properly overcoated with gloss which will seal out the moisture.

Filling holes with filler is really a waste of time. The fact that you are considering it in the first place probably means that you don't really want to spend much time or money on the job - and sadly the old adage - you get what you pay for - applies here. It will look fine for a little while - then the metal around the hole will rust through again. The reason is of course that the rust has come through but the surrounding metal has thinned and is probably still unprotected on the back - and so will rust through quickly.

Phosphoric acid is used as the basis of many rust cure products - and also is the basis of many etch coats which are always used to get good adhesion on alloy and is increasingly popular for use on steel. On alloy it penetrates the thick oxide layer and grabs hold of tthe chemically roughened surface. If you don't use it the paint will flake after a short while and it will probably have to be stripped. Some synthetic primers will stick quite well to alloy as well. (Synthetic is the paint process generally used for commercial vehicles as its slow drying and enables the sprayer to work with a large wet edge which is needed for large objects. Synthetic paint actually brushes beautifully for this very reason and is available in many car colours including metallic I think.)