There are two types of ZINCALUME® steel. If you must get a rainwater tank in this material, then ensure you get the most recent generation. “Next Generation” ZINCALUME® steel (AM125) launched in August 2013 and lasts longer than older ZINCALUME® steel (AZ150).
Both are normally used in roofing, but can be found in steel tanks. BlueScope extended the roofing warranty on ZINCALUME® steel AM125 up to 33% longer than its older form (AZ150).
It is important to note that ZINCALUME® is incompatible with lead and copper, treated timber, uncoated steel, fertilisers, pesticides and abrasive cleaners which can all cause corrosion.
AQUAPLATE® steel is what BlueScope recommend for rainwater tanks made from their steel sheeting.