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Thread ID: 115276 2011-01-11 01:24:00 Garage Door Re-painting bk T (215) PC World Chat
Post ID Timestamp Content User
1168725 2011-01-11 01:24:00 Sectional metal garage door needs to be repainted before the rust eats away the whole piece.

Does it require undercoat or just paint over the existing paint?
bk T (215)
1168726 2011-01-11 01:38:00 Is it already rusty? I would give it a coat of kilrust I think by Watyl gary67 (56)
1168727 2011-01-11 01:43:00 Is it already rusty? I would give it a coat of kilrust I think by Watyl

Yes, some surface rusts, which (I think) can be removed with sand paper.

'Kilrust' can stop rusty surfaces, or the rusty surface has to be removed first?
bk T (215)
1168728 2011-01-11 02:49:00 "Sand paper" is used on wood not metal :)

Rust kill type products contain phosphoric acid which combines with rust to form iron phosphate, an inert coating.

Phosphating is used as an industrial protection coating method for nuts and bolts, guns etc, one system is called Parkerizing.

If the rust is too thick it should be removed as otherwise the converted phosphate may detach from the steel surface, but not every bit has to be, the rust kill will do the job.

Then there are special oil based undercoats to use on phosphate treated surfaces which are supposed to help prevent further rusting, Goldex Rustkill and British Paints Stop Rust were/are two varieties.
Terry Porritt (14)
1168729 2011-01-11 02:53:00 Get a can of CRC Zincit or similar zinc based primer (car primer would do) to put on AFTER you sand the patches of surface rust off ... then just paint as usual. If some of the paintwork is still nice and shiny, take to it with some coarse steel wool to take the shine off and help the new paint adhere. SP8's (9836)
1168730 2011-01-11 03:00:00 Actually there is a liquid rust kill that you brush or spray on that neutralises the rust ... it can get into the crevasses where you can't reach with sandpaper ... then wash it off before painting.

And I think Terry is correct ... is it some type of acid ... hence the washing off after application.
SP8's (9836)
1168731 2011-01-11 03:06:00 OK. Thanks for the info.

Should I use oil-based or water-based paints? Oil-based takes a much longer time to dry and very messy to clean up though.
bk T (215)
1168732 2011-01-11 04:50:00 I think originally doors like that have been powder coated
Having them redone like this would be much better but it may cost
Lawrence (2987)
1168733 2011-01-11 07:37:00 "Sand paper" is used on wood not metal :)
It can be used on metal too as they have grades for it.
mikebartnz (21)
1168734 2011-01-11 08:14:00 It can be used on metal too as they have grades for it.

I'm old fashioned, in my day sandpaper was the name given to glass paper, for wood finishing, now it seems to be used more generically and incorrectly.

Emery paper and silicon carbide papers etc were called just that, not sandpaper. The silicon carbide papers and the red "jeweller's rouge" papers tended to be used industrially for metallurgical polishing and were not so common as today.

Years ago emery paper was the most commonly or only available abrasive paper from hardware shops.
Terry Porritt (14)
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