Metal Electrical Conduit - can I paint it?

[Lemansky]

We are having the box room plastered but running up one wall is a floor to ceiling, metal, electrical conduit. The plasterer hasn't been able to cover completely.

So can I paint it, when we get to decorate the room, and what's the best way to go about it? The previous owners had wallpapered over it, but it didn't look great and seems to have gone a bit rusty, probably to do with it's age + the wallpaper paste...I hope it's nothing more sinister, too late now anyway!

[lalalonglegs]

Yes, you can paint it. You'll need to rub down the rust and then use a primer.

[Lemansky]

Brilliant, thanks very much.

[Lemansky]

Just to return to this, we had the room plastered and the plasterer skimmed, very thinly, over the pipe and then painted it with the mist coat. This happened in mid april.

We're going to paint the room next weekend and I noticed today that the rust has started to seep though the paint. I have a tin of Zinsser B.I.N primer-sealer stain killer which we brought for another job.

Will that be ok to use and solve all my problems, or is there anything else we need to get?
Thanks!

[PigletJohn]

I suspect condensation. Is the room or wall damp?

If it is the incoming supply, on the way to the meter, it should not be concealed under plaster. It would be very undesirable if somebody put a nail or drill into it.

[Lemansky]

It's not damp anywhere in the room as far as I can see, definitely no signs of damp and there weren't any before it was replastered. The heating comes on when necessary due to the thermostat and I've got the air brick open and it has been since we've moved in. The room's been empty since it was replastered and had the mist coat done. It's a terraced house and it's on dividing wall between houses, so not external.

I think it's the mains into the house, but it's definitely not concealed under the plaster, you can see it very clearly so we definitley won't be drilling into it.

[PigletJohn]

perhaps it was the water content in the emulsion paint and the wet plaster. It is better to paint ferrous metals with an oil-based primer and undercoat.

You also get rust marks if you have old steel screws or nails near the surface, and fill over them with polyfilla or similar which contains water.

[Lemansky]

That would make sense I think. Is the Zinnser primer mentioned above ok for the job?
Thanks.

[PigletJohn]

depends if it is water or oil based. Oil (thinned with White Spirit) is OK. Some Zinsser products are thinned with alcohol (meths), and I don't know that would work. They have a good Help Desk.

Red Oxide Primer is cheap and works on rusty steel. Other metal preservative primers can be very expensive, you will find the tins unexpectedly heavy. I use a Dulux Trade one, it may not be in High Street shops and is very thick. Don't use Hammerite. Sand it first. Apply two thin coats.

[Lemansky]

Brilliant, thanks. I will investigate the Zinsser and if it's not suitable I will have a look at your other suggestion.

[Greenwolf016]

www.screwfix.com/p/no-nonsense-zinc-galvanising-spray-paint-silver-400ml/40801

Use this, I use it externally on installations. 👍🏻

[MrsFlorrick]

If you had the pipe skimmed over (galvanised). The water content of the plaster being placed directly on it will have caused a little surface rust. This will then bleed through the plaster and cause the stain. Not condensation.

The pipe should have been painted first with a metal paint to seal it to prevent this.

It's likely the current staining won't increase as the plaster is dry. So zinsser should be fine.

[Lemansky]

Thanks, that's very helpful to know.