Why Galvanised Steel is better than Zincalume

Galvanised to last longer than ZINCALUME steel


Today, there are other suppliers of poly lined steel tanks, many claiming that ZINCALUME® steel will outlast Galvanised materials in this application. Simply put, this is not true. When a tank is full, the liner is pressed up against the inside wall, causing condensation to be trapped between the liner and the tank wall. The corrosion to ZINCALUME® steel is inevitable due to the moist conditions & the lack of oxygen (air), which ZINCALUME® steel requires to form its stable oxide films that would normally prevent further corrosion.

For example, ZINCALUME® steel roofing & wall cladding on a shed will out perform Galvanised steel because the steel is able to “breathe” (form its stable oxide films). However, if the ZINCALUME®  steel wall cladding comes in contact with the ground rapid corrosion can occur. This is due to the moisture in the ground and the fact that the steel is unable to breathe. That is why shed manufacturers use only galvanised steel for the posts which will be buried ie moist conditions and unable to breathe. The same example is found in fencing and all other structures made of steel. There is one overriding reason why some tank companies promote ZINCALUME® steel in this application, cost. On average Galvanised coated steel costs 33% more than ZINCALUME® steel. This is because the Galvanised material  has a minimum Zinc coating of 450 grams/sqm whilst ZINCALUME® steel only has a minimum Zinc/Aluminium coating of 150 grams/sqm. That’s 3 times the coating mass of ZINCALUME® steel!

Another reason is because they can offer a range of colours using the same cheaper AZ150 coated material roofer’s use when they supply a bull nose verandah. If you’re still not convinced Galvanised material would outlast ZINCALUME® steel in a poly lined steel tank then we suggest you obtain independent advice. Ask a traditional tank maker, a shed builder, a fence contractor or a corrosion engineer as to why they would use only Galvanised material in an enclosed moist environment.