I have a metal roof that is totally rusted but seems to be structurally sound--no leaks. However, I am worried about the future. Can I sand and then coat this metal roof and expect the fix to last a few years, or do I need to replace the whole thing?
Eventually, no doubt. I took an old machine shed and sprayed one of the rust converters primers and then painted. That was old (70-80 yr maybe?) heavy corrugated galvanized, not recent 26 ga, stuff however, so it is still much heavier than typical new "tin". It's been about 5 years now and is holding up well and the light color makes for noticeably cooler interior during hot summer.
Whether for house/light current roofs it would be cost-effective I don't know--it wasn't a whole lot less than new tin, but new tin would have required adding extra support in this case and that was the deciding factor for me.
I initially intended to simply pull the sheets and turn them over since the inside face is good as new, but after starting in it became apparent that it would have taken essentially the whole winter... :(
When I bought my farm there were several sheds that had galvanized corrigated tin roofs. All had at least some rust, and one was almost entirely rust. Yet, all were solid and had no holes. I just bought a
5 gallon bucket of silver "aluminum paint", and coated the whole roof using a roller and paint brush. I did no surface preparation, other than removing dead leaves and junk, and hosing it off the day before to remove any dirt. I also pounded down all loose nails and added a few (neoprene washer nails), where needed. One coat of paint and 5 years later it is still mostly fine. However, last summer I bought a few cans of cheap silver spray paint for a buck a can at Walmart and touched up the few spots that were showing a little rust again. Maybe in a year or two I will paint the whole thing again just for protection. The total cost was about $80 for paint, rollers, nails, clear silicone caulk (used after painting to seal around loose nail heads). Sure beats the cost and labor of a new roof.My animals and hay stay nice and dry...
Mark
Once something gets a protective coat of rust, it takes a LONG time for the remaining material to oxidize (decades, most likely). For example, you will never see a barbed-wire fence (rusty though it may be), "rusted through."
For example, Aluminum oxidizes very quickly. Looking at a soda can or a bit of foil, what you see is Aluminum oxide.
In your case, what you want is to keep the protective Iron Oxide coating in place so as not to expose any of the original material to the elements. I would think a paint job would be sufficient - the paint not to protect so much as to immobilize. And look pretty.
Sure we have. You just ain't old enough or seen enough. But I do agree that it took a long time. I think.... .
Andy comments:
As a man gets older, his barbed wire is the second thing to go......
Andy
....
Depends on the definition of "long" and the location...in a lot it may not take very long at all for lower strand(s) to fail...
Generally true about the red oxide. In fact, road guards are often just coated with the red oxide in parts of the country and usually get smashed up before they ever get eaten up with rust.
However, the op is talking about roofing which is very thin. I've seen plenty of metal roofing and siding of corrugated steel that is pitted with lots of holes).
Again you are correct about leaving the rust there and just painting. Apply a rust primer and then an aluminum, or better a zinc, rich paint. There are specific paints made for this purpose that will last a long time. Not cheap though.
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