Raw steel gutters…which product to coat the inside?
brandons
| Posted in General Questions on
I had gutters fabricated out of raw steel for my project. What’s a good product to use to coat the inside of the gutter to prevent rust? They are 18 gauge raw steel and we intend to leave the exterior of the gutter as raw so it will patina/rust.
Thanks,
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Replies
brandons,
I would use an elastomeric product like Tuff Coat. I don't want to be discouraging, but hopefully you are in a dry climate. Galvanized gutters last about a decade here. 18 gauge raw steel would be gone in maybe three.
Definitely something that has body of its own. Maybe even peel and stick membrane, although it might be tough to keep it from puckering. Anything that relies on just adhesion like paint would wear off quickly.
Ditto on raw steel not being durable. It would also stain the facade of the building.
Maybe wrap the back to keep the staining[and I think rot] down. I have some accidentally exposed grace IW on the north side and it hasn't peeled up in 13 years. The kind with the non skid coating might last longer in the sun if it will bend the 'wrong' way, you could wrap part of the [outside]bottom too without lettering showing, keeping staining down again
18 ga [.049]will last a while I guess but sure wouldn't be my first choice.
I would try spray applied bedliner here. This is a very tough material that should also withstand sunlight fairly well (use a black version for best UV resistance). To give you an idea of how tough this stuff is, I have a customer hat heat treats steel parts and they used bedliner to line the hopper of a cleaning machine. This hopper has several tons of what are basically large steel bolts bouncing down it for hours every day. They have gotten several years out of it so far.
The problem you’re likely to have is that as regular “plain” steel rusts, the rust is an oxide layer that falls off, exposing new steel to rust. You’ll end up with rusty flakes falling off and ultimately you’ll have rusted through holes that will leak. Leafy gunk that will build up in the gutters will tend to make the problem even worse, since that stuff seems to make steel rust out much faster.
Normal plain steel doesn’t form a patina the way that copper does. The oxide layer that forms on copper adheres to the underlying base metal, so the oxide layer acts a protective layer to prevent further oxidation of the underlying copper. Aluminum reacts the same way. There is a type of steel where the rust adheres, and it’s known as “corten steel”. You often see wind chimes made from this material, and I’ve seen street lamp poles made of it too. If you want rusty-looking gutters that will last, I would look into using corten steel. I would not use plain steel here.
Bill
If it were me, and they were already manufactured, I just leave them be. There's really no coating that you're going to be able to use that will stand up to the amount of water they are burden with over their useful life. Even if so, the corrosion will happen from the outside in, eventually leaving the coating as the structural component.
When you replace them I'd do as Bill suggested, and use corten steel if you like the look. Otherwise copper or another inert metal if you decide to go back to the traditional feel.
Seems like a waste of effort to my ear. Raw steel seems likely to have started rusting already. Applying any coating to a rusty surface seems unlikely to prevent rust. It could be argued that when water gets under this coating the steel will remain wet longer because the water is now trapped and the coating slows evaporation.
If you must try something try Fluid Film.
https://www.fluid-film.com/
I hope you have thought thru the rusty patina idea.
The water coming out of the downspouts will stain every thing it comes in contact with.
Their will be a rusty line below every gutter from the water that drips off the gutter.
Walta
If you want the exterior to have a patina, some coats of automotive grade 2 part urethane clear coat after letting them sit for a bit in the weather. This will help slow down further rust for a while. Interior of the gutter, you could use epoxy primer followed by clear coat.
They are already fabricated. I went the Bedliner route as Bill suggested. We’ll see how they hold up.
Thank you for the suggestions