kickinit wrote: Wouldn't have clue on price but polypropylene would work. I would guess the price would just be too high. It would actually be interesting to see the price comparison between buying s/steel over aluminium. The best way would to be just go with galvanised, but don't make the mistake a lot of people do and not protect the ends you cut. The best thing is if you don't like the colour go to bunnings get some paint, if you have a colourbond roof they can match the colour as well.
Spray Galv is a wonderful thing for awkward spots after the event, but a good old galv coat applied with a brush is better economics.
The problem is making sure nobody skips that step if you don't do the job yourself...
I have the same concern about steel framed houses - whether your builders staff bother to do anything about cut ends and drilled holes.
I fixed the recurring rust on the external mirror frames of an Alfa I owned in the late 1980s with spray galv and spray gloss paint when it had recurred twice after being allegedly treated each time by the dealer under warranty.