Understanding Steel Differences When It Comes To Rainwater Tanks

Understanding the Difference Between ZINCALUME® Steel and Galvanised Steel in Steel Liner Water Tank Construction

When shopping for your next rain water tank, you will be presented with a number of options—from size to colour and beyond. There is a lot of information to process depending on the location and application of your intended tank.

One such decision includes choosing the right material for the construction of your water tank. When shopping different manufacturers, you may see materials listed such as galvanised steel or ZINCALUME®. Many consumers and business alike may be confused about the differences between the two materials or believe them to be the same thing, when in fact, there are major differences between the two types of steel. This article will give you all the information you need to choose the best material for your water tank installation.

Galvanised Steel As A Water Tank Option

Galvanised steel is a common material you may see listed for the construction of your water tank. To “galvanize” steel simply means to apply a protective zinc coating in order to prevent rust. The most common method is hot-dip galvanising, in which parts are submerged in a bath of molten zinc. Galvanisation as a coating technology was developed in the 1830’s, over 180 years ago.

Galvanised steel’s application in water tanks has also been around for many years. The zinc coating on the steel (galvanisation) is considered a “sacrificial coating.” Sacrificial coatings are so-called because they are placed on the metal for the purposes of succumbing to corrosion first. Since all metals have the potential to corrode (called “activity”), when steel is coated with a more active metal, the active metal will corrode before the steel—the primary tank construction material—and provide protection for the tank from corrosion.  Sacrificial coatings are effective even if the steel substrate is exposed based on electrical conductivity. Sacrificial coatings physically migrate to a corrosion site to provide protection. Galvanised steel relies mainly on sacrificial protection to resist corrosion.

While galvanised steel has been a safe and effective choice for water tank construction for many years, whether for drinking water storage or rainwater collection, it is now considered outdated technology for the construction of steel liner water tanks since the advent of ZINCALUME®.

Incorporating ZINCALUME® Steel Into Your Rainwater Tank Choice

The most modern option for steel liner tank construction today, ZINCALUME® steel sets the standard for corrosion resistance and long life. ZINCALUME® steel was launched in 1976 after extensive research into ways to improve the performance of typical galvanised steel. By blending aluminium with zinc in an alloy coating, researchers discovered a way to greatly enhance corrosion resistance, and BlueScope Steel researchers developed the production process. The result of this extensive research and development brought a next-level material for water tank construction to market with a lifespan of up to four times that of ordinary galvanised steel.

In 1994, second generation ZINCALUME® steel was launched, featuring the addition of a resin coating that improved mark resistance, and made the steel easier to handle and roll-form.

 

In 2013 BlueScope developed next generation longer lasting Zincalume steel. Setting a new industry benchmark, next generation ZINCALUME® steel meets the growing demands for increased durability, resilience and sustainability.

 

Next generation ZINCALUME® steel’s patented Activate® technology introduces magnesium into the aluminium-zinc alloy coating, improving galvanic protection by activating the aluminium. The result is a tougher protective coating that’s more resistant to scratches and scuffs encountered during construction.

The protective coating innovation also increases the product lifespan of next generation ZINCALUME® steel whilst using fewer metal resources. Compared to ZINCALUME® steel AZ150, next generation ZINCALUME® steel AM125 has a smaller environmental footprint in all 18 Life Cycle Assessment (LCA) categories assessed.

 

While ZINCALUME® steel has many industrial applications, its use in water tank construction is the perfect application for the metal’s superior anti-corrosion properties. Water tanks constructed using ZINCALUME® steel can provide a life expectancy in excess of 25 years.

BlueScope describes the three-way mechanism used by ZINCALUME® to protect the steel substrate. First, the aluminium component of the coating provides a tough physical barrier between extreme atmospheric conditions and the inner core of steel. Second, the zinc in the coating protects the steel at cut edges and scratches. Galvanic action causes the zinc compounds to automatically build up at cut edges and around scratches through an electrolytic reaction when water or moisture is present. It slows the rate at which the surrounding coating is consumed around exposed areas. This effect is sometimes referred to as the “self-healing” property of coatings containing zinc. Third, the magnesium activates the aluminium to increase corrosion resistance by restricting corrosion pathways to the base metal.

So, while galvanised steel and ZINCALUME®  both provide sacrificial protection, only ZINCALUME®  steel provides a second layer of defense by also acting as a superior physical barrier to corrosion of the steel substrate.

Insist on ZINCALUME® Steel For Your Water Tank

Due to its lower cost, consumers and businesses may initially be tempted to consider simple galvanised steel over ZINCALUME®; however, galvanised steel is a false economy when you consider the earlier need for replacement and increased risks from corrosion of ordinary galvanised steel.

Pioneer Water Tanks has been manufacturing water tanks, and water tank liners for 30 years. Originally relying on galvanised steel for the construction of its tanks, Pioneer now exclusively uses ultra-modern next generation ZINCALUME® steel due to its superior performance within the water tank environment.

Other manufacturers trying to sell consumers and businesses on inferior galvanised steel tanks may try to convince you that the corrosion rate of  ZINCALUME® steel compared to galvanised steel is the same; however, the longer life of ZINCALUME® steel is attributed to the rapid slowing down of this corrosion rate shortly after the initial exposure to the environment. According to BlueScope Steel, because the coatings on galvanised steel and ZINCALUME® steel perform in different ways, ZINCALUME® steel has much better corrosion protection (and service life) than galvanised steel. Side by side exposure testing has shown corrosion protection provided by ZINCALUME® steel with an AM125 (125g/m2) coating mass is far superior to that provided by galvanised steel with a Z275 (275g/m2) coating mass. The tests demonstrated that ZINCALUME®  steel corrosion protection can last at least four times longer than the corrosion protection provided by traditional zinc coated steels in roofing and walling applications in identical environments.

So, there is absolutely no basis for other water tank manufacturers to try to convince you that galvanised steel and ZINCALUME® perform to the same standard.

COLORBOND® steel is a pre-painted version of ZINCALUME® steel, so it uses the tough and durable ZINCALUME® steel as the substrate before receiving three layers of additional coating technology, comprising a pre-treatment layer, an oven baked layer of corrosion inhibitive primer, followed by a topcoat of specially developed, exterior grade paint which is again oven baked to provide resistance to chipping, flaking and blistering to ensure the finish retains it look for longer.

In addition to insisting on the use of ZINCALUME® steel and COLOREBOND® steel for the construction of all water tanks, Pioneer Water Tanks also employs additional state-of-the-art engineering to further mitigate the risk of corrosion of its water tanks.

The Bottom Line When It Comes To Tanks

The purchase of your next rain water tank is a major investment and an important decision that should not be taken lightly. It’s important to understand all your options and their effect on the lifespan of your water tank.

Quality construction standards using state-of-the-art materials and methods can extend the lifespan of this major investment and ensure top, problem-free performance for the next 20 years and beyond.