Rust prevention on window flashings

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SeanC3

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#306009 20-Jun-2023 12:02

We're about to repaint around our windows as the flashings are showing rust through their current paint.

When they were last repainted about 4 years ago, the painter scraped the flashings down and applied red primer then painted with same paint as the wooden window structures.

I was hoping someone might have suggestions for alternative (DIY) treatments that might last longer than 4 years. The internet offers lots of suggestions but no personal experience :)

cheers

Bung

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#3092471 20-Jun-2023 12:34

We are about 400m from high tide. I have some rusting galv flashings a heavy coat of spray zinc about 5 years ago. The rust isn't showing yet but I am replacing the flashings just because I have a lot of powder coated alloy flashing.

timmmay

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#3092472 20-Jun-2023 12:35

I had the rust treatment done multiple times. In the end I had all the flashings removed and replaced with aluminum flashings about three months ago, since aluminum can't rust, it's oxide is clear. Stainless steel is a good option as well, it will rust eventually though.

mdf

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#3092486 20-Jun-2023 13:18

As others have said, replacing with something like aluminium or coloursteel is probably the first best option. In all likelihood, the rust has spread to areas you can't get to it (e.g., under the weatherboard) and it will spread back from there. The thin metal also means you don't have a lot of meat to work with. And I suspect that if they have been scraped previously, some of the galvanising probably went with it.

That said, if you've gotten on to it early and/or cannot replace, I would:

Scrape/sand back to bare metal
Apply rust converter (I tend to use CRC brand, but mostly out of habit; I'm sure other brands will perform similarly. I wouldn't use a spray/rattle can for this, they always seem to clog)
Apply zinc primer (see previous comments re brand). Note that even this stuff only advertises "6 year protection".
Apply epoxy enamel top coat. CRC has a black option here but I've recently started using White Knight brand and have been impressed with this. Probably not strictly required if you're topcoating with house paint (see next step) but will probably (?) bond better with the zinc primer.
If needed/desired, overcoat with house undercoat and topcoats.

neb

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#3092806 20-Jun-2023 22:09

Another option if you want to coat lightly rusted metal directly is the petrolhead's secret weapon, Flood Penetrol. It's self-levelling so flows into areas you can't directly get to, soaks into the rust, and forms a hard varnish-like surface coat after a few days curing time. There's plenty of stories, unfortunately all anecdotal since Flood don't sell it for this purpose, of stuff being left out for years in the weather without degrading further.

Oh, and a much cheaper option than any rust converter is to buy a 1L bottle of phosphoric acid, which is the active ingredient in rust converter, dilute it down, and use that.

Other than that, everything @mdf said.

fe31nz

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#3092821 21-Jun-2023 00:57

After cleaning off the rust, you could try marine grade paint. We used that for our 1975 vintage corrugated iron roof and it is lasting very well. Previously we had never painted the roof and it had lasted very well, but if finally started to get some rust spots. The marine grade paint went on 10 years ago (after rust treatment) and so far no further problems.

SeanC3

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#3092829 21-Jun-2023 06:56

Thank you very much for all the suggestions. Much appreciated.