Used galvanized roofing ?????

gmccool

Well-known Member
I have some used galvanized roofing tin. It has set outside for several years & has gotten wet between the sheets & has some white chalky stuff on it. I am told it is called white rust. I was hoping to use it on a roof. Will this white rust come off or will it get worse. Should I use it as is??? There are very few nail holes in it & I can put screws in the old holes so that isn't a problem. Or should I just throw it away & buy new. There are probably 60 sheets 30' long. Thanks Gerald
 
How old is old & what is your time worth? Truly old tin was heavier gauge than the later stuff. It was already much thinner by 1990. I have barns built in 1970s with then-old tin that are still in use today. I have barn built in 1992 with new tin that is rusty as can be. We gamble.
 
I'd use it but then I do not throw much away. I'd put it up then use a roof coating on it and be done with it. Why throw away something that can be used?? That is one of the big problems with people now days they look at something and if it is not perfect they throw it away
 
old, what roof coating product have you had good experiences with? I have a bunch of run-in sheds for horses that could use a coating, but I never figured out what product was worth the cost
 
Well again I use things like oil based paints that I pick up cheap at yard sales and that type of places. Again I am cheap so I buy what most would throw out and make it work. I have found a good heavy coat of an oil based paint on a roof will last for years and if you find it at the right place is cheap
 
old, that makes sense. However, in my case I have old roofing that I pulled off a building and wasn't able to reuse the screw holes. Anybody have any experience with one of the thicker products ? My goal is to seal up the rusted areas and help hold the caulk in the holes.
 
I think the chalky stuff is caused by a chemical reaction between the water and the zinc in the galvanizing. I would clean it good and as others suggest, apply good coat of paint.
 
Australia is pretty much known as the land of galvanised iron. I have recycled it many times. The roofing on some of my sheds must be close to 100 years old.

Before good silicon sealers became available we would use solder to repair nail and screw holes. Now a bit of silicon and the job is done.
 
Rub off the worst of the Zinc oxide with a damp rag and then wash with a 50% vinegar/ water solution , follow up with warm soapy water . Dry off the area treated and let sit outside for a few days to a week depending on the dampness of the atmosphere . If there is a development of red rust on the affected areas this shows that the surface coating is compromised and nothing short of priming and painting will make it serviceable.
 
I would put it up and paint with aluminized roof coating after a few rains washes it. 5 gallons of that stuff goes a long way. I thin it a little with kerosene to make it brush on easier with a brush on a long handle. They usually sell the brushes right where the paint is.
Use once and throw.
Richard in NW SC
 

I'm with Charles in Aus. Any acid will remove that oxide. If there is ANY rust you need to acid wash. They sell gallons of Phosphoric at the big box stores. The phosphoric acid will convert rust if it is not too thick, to inert iron phosphate. Painting or coating of any sort must be put on a clean rust and oxide free surface, or it will protect the rust and help it to work faster by holding moisture in. Sure it looks good for awhile but the life is greatly reduced.
 
Don't give it a second thought and use it. 40 year ago new got that way before it was installed and it is still good today.
 
In that case I fill the holes with a silicone caulk and then paint over the whole thing. On most I try to use a white or light colored paint to cut down on heating by the sun
 
I think the white stuff is a form of zinc oxide, the same material used to galvanize the tin.

Zinc oxide kills mold on shingles. look for a galvanised riser pipe coming out of a shingled roof. Then, look below the pipe and the shingles look new, the rest of the roof looks dirty.
 
Silicon should bond to galvanized steel,(sealing old fastener holes and heads of new fasteners) but remember silicon is NOT compatible with Bituminous/Asphaltic materials. So if you are going to use an asphalt roof coating/paint, (silver roof paint) you'll need to seal those holes first and not mix the 2 or try to bond one to the other. Once that roof paint is on there, you'll have to clean it off anywhere you want to use silicon.

Certainly does not negate the use of 2nd hand materials, something I'm a big fan of, its just good 2 know about these 2 materials per the above. I've had this discussion regarding our old barn with metal roofing, the older half, it fell on deaf ears.
 
For a coating I use house trailer roof coating and put it on with a roller and long handle. Buy a good paint stirring attachment for a 1/2 inch drill(strong and slow). It goes on fast and will last for years, as long as it was grease free. A little rust seems to hold better than shiny roofing.
 
(quoted from post at 15:43:30 06/30/15) Remember to turn the good side out and the weathered side in.

Fine if you use it for walls , in the old days you could solder up the holes in Galvanised iron so you could use it on roofs . Turning it upside down on a roof puts the fastener hole on the bottom of the valley . I don't know if silicone would be totally reliable if used in that situation . Old iron probably makes up more than fifty percent of cladding on farm buildings here .
 

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