Hey Gary, Sorry I only just saw this thread, We get our sheet from bluescope, but any of the big suppliers can sell you some.
We use 1.0mm cold rolled sheet for fabricating patch panels as its much much easier to form then hot rolled, we also keep 1.6mm and 3.0mm in stock for the heavier duty stuff (chassis rails etc) but this is hot rolled
We also coat all of our sheets in a POR-15 product called SW-2 http://ppcco.com.au/coatings_sw2.htm to stop them from rusting and it lasts a long time as you dont use much at all, West Coast automotive supplies sell it
(08) 9376 4888
There is nothing better then working with nice clean steel... if its only very light rust you can pretty much wipe it off with some Ranex http://www.bondall.c...Rustbuster.html Ranex itself when wiped on a sheet will stop any flash rusting for quite awhile... we use SW2 tho as you can paint straight over it without having to worry about neutralizing it, Altho even still we wizz the panels with a orbital anyway before spraying primer.
Or yea you can just sand the rust off... but if you leave the panels for too long they will start to pit abit and takes longer to sand and you are just thinning out the material so its better to protect it and prevent the rust rather then try fix it later.
I hope this was helpful let me know if you have any other questions.