galvanised roof sheets rusting

[knockavacca]

hi, my 12 year old garage roof is showing several patches of rust,i thought that "galvanise" was not soposed to rust,can anyone offer any suggestions please

[redcrx]

Galvanised is just a zinc coating which will disintegrate instead of the steel at first. Eventually the zinc may all go in the places where water collects and the steel will then rust.

[knockavacca]

redcrx, thanks for your reply,in my case there is NO water collection as the water flows off the roof as it lands so any other ideas appreciated thanks again

[scotman]

have a look here

http://www.slecladding.co.uk/galvlife.htm

[The Builder]

Probably the old story Knocka ........... the cheaper the sheet, the thinner the zinc coat is likely to be.
To back up what Red has said, it only takes a minute scratch in the zinc to get back to the steel sheet.
Interesting link from Scotman.
There are lots more alternatives today. Try powder-coated box-profile sheets. Nice colours, looks a bit groovier than corrugated.

[knockavacca]

thanks to you all,final question ?, what would be the best paint to use (if any),to treat the roof without havintg to replace it many thanks

[The Builder]

Here you are Knocka ..........................

http://www.decorating...viewprod/t/TORGALVPF/

[knockavacca]

many thanks to all espcially "the builder",ill give the paint a try cheers

[AlBags]

Rainwater is mild acid .. Water will eventually cut channels through lead.
It is just wearing out.

[KARL]

A scratch on hot dip galvanised steel is self healing but eventually the coating will corrode away in patches. By far the best material for replacing the zinc coating in your case (and any similar, or even starting from bare steel/iron including mildly rusted) is Galvafroid by Fosroc. This is available from well stocked suppliers in a small tin as well as larger ones. Just be sure to follow the instructions on the container. It is not cheap but it saves a lot of alternative expense and it lasts ages. Otherwise what you can do is use good ordinary paint, preferably with a primer for zinc surfaces first, such as already suggested.

[AlBags]

Basically cold Galvanising.

[dazarooney]

I had a similar issue but got my cladding from the link below, it's been great:

http://www.cadischmda.com