Then along came ZincalumeŽ, a high tensile roofing product that revolutionised the roofing industry, it was strong, came in long one-piece sheets that reached from the roof ridge to the gutter without a join.
The emergence of ZincalumeŽ (primarily a zinc and aluminium mix of metals "galvanised" to steel) as a popular roofing material brought problems for the trusty galvanised water tank. In the early days there were instances where new ZincalumeŽ roofs were installed and within months the galvanised water tank had rusted out. The tank would break out in brown freckles and in a short time the freckles would begin to join up and the tank would collapse and the owners would then realise that the freckles were rust. The freckles/rust were caused by electrolysis. Electrolysis is a result of metals of opposing make up being joined together, in this case with water, which then creates an electrical field like a battery. The electrolytic action corrodes away the less noble of the two metals and in this case the galvanised tank.
Nowadays electrolysis is still possible where a building still has a galvanised (zinc) roof which supplies water to a ZincalumeŽ tanks.