Rust repair/filing/priming/painting - how best?

[Matt Tomkins]

hi again,
i'm now coming to the stage with my moggie where i need to repair the surface rust.

what would anyone recommend in terms of:
1) rust killer
2) primers - red oxide and/or grey primer?
3) the best place to get hold of smoke grey pain in a tin - so far i can only seem to find the aerosols, though i planned to spray the thinned canned paint through an airbrush.

many thanks

matt

[davidmiles]

Hi Matt, your airbrush may not have the volume needed, but the compressor might be able to cope with one of the low pressure high volume spray guns available. Have you considered acid etch primer from a spray can, goes on and etches itself into the surface of the steel as prep for standard primers.
Ive heard rust stop is a good professional product from frosts, I plan to get some but so far Ive only used krust from Halfords, it etches rust and chemically stabilises it into black metal, so far so good, as I've not had any rust recuring throughout this damp winter we've had. But I don't think its a professional product.

[chickenjohn]

Don't use any "rust killer" products, they are all basically rubbish! The only way to deal with rust is to get rid of it!! Especially in a visible panel area. These products that turn the rust black only work for a few months. Scratch the black "converted" surface (not really converted, just covered) and you will see brown rust still there underneath.

After the rust has been completely removed, I would spray the bare clean metal with etch primer, followed by high build primer. Then when dry, sand the primer to thoroughly feather the repair into the original paint. You can for small areas (a few square inches) use an air brush with cellulose paint thinned ~75% thinners 25% paint.

(Normal spray gun is 50%: 50% cellulose paint: thinners)

[Matt Tomkins]

great, thanks alot

[Matt Tomkins]

i think the reason rust killer products don't seem to work is chemically simple

the active ingredient in these product is phosphoric acid: H3PO4
the rust to be converted: iron oxide: FEO

H3PO4 + FeO --> FePO4 (iron phosphate) + H2O (water)

- i wonder what is going to happen?!!

[bmcecosse]

The water evaporates - Simples! ........ They do work - to kill off any lingering surface oxide - but they are not of course a cure for a panel that is rotting through from the other side!