Outdoor metal paint

[hewhowalksamongus]

Hi,

I am a little upset because I sanded off and re-painted my metal stairway running upto my flat.

How should I protect my metal work which seems to rust too quickly?

I think I did this about 4 years ago and still have some of the paint in working condition in the shed.

But the paint has already started bubbling and flaking off when the main angle irons underneath holding a large concrete slab.

I guess the reason is because the area under the slab cannot be accessed and cannot be painted so water will always be able to reach the bare metal. from the other side.

Last time I used a yellow zinc primer and a hammerite black top coat. My decorator recommended maybe using a chromium based red primer.

Any thoughts? so I don't have to do this again in another 4 years.

Thanks

[Adrian]

If the paint's "bubbling and flaking", that sounds like it's coming through from underneath, so the root problem wasn't the paint but the prep.

Once you get it back to bare shiny bright metal, give it a coat of rust converter (I've not heard anything but good about Vactan), THEN a good primer, then a good topcoat.

BTW - Hammershite is, well, s**te.

[hewhowalksamongus]

Thanks I have been reading a bit on other sites about car body rust. I am also treating a classic car in my garage with simitrol which is basically waxoyl.

It seems because I cannot get to the top of the metal angle iron as it supports a ton of concrete I can only get to the bottom. After cleaning the rust will always come back because the water will sit at this point. Maybe a deox-c type treatment. But no much use just spraying and hoping to clean everything.

I am thinking the best I can do is a bit of hydrate 80 type sealant followed by a heavy zinc primer. I've seen warnings to go for a high zinc content primer as modern primers have started to scrimp. I am hearing bad things about modern imitation red lead paints.

Any recommendations? The vactan was interesting but perhaps not good to overcoat onto rust only onto clean metal.

[Nightjar]

You could try fitting sacrificial zinc anodes, as used on boats. They should prevent the steel from rusting, which, I presume, is the main point.

Colin Bignell

[Theo Markettos]

Could you attach a piece of zinc here to give cathodic protection? I suppose the issue would be the water would need to touch both the zinc and the steel to complete the circuit - dry zinc and wet steel is just the same as wet steel. But if you managed to, say, wedge in a bit of zinc between the metal and the concrete it might help?

Theo

[Rick Hughes]

The bes approach would be to blast etch it back to bare metal (even a simple pressure washer kit would do it) or use a jelly paint on rust converter ... Kurust, etc.

Then a really good etch prime. eg

On top if you ant it to last a 2-part metal paint. eg

[Dave Liquorice]

Thought Hammerite was self priming. ie clean back to a firm base and apply. The gate hinges I did several years ago are fine, surface prep was no more than a good wirebrushing. But the stuff is a bugger to use, tiny bubbles form very easily and unless you get the second coat on within the specfied time period (a few hours) or wait (weeks?) they will leave tiny pin pricks in the paint film that will lead to rust underneath and blistering.