Galvanised vs Zincalume Tanks Lifetime Ownership Cost

Looking for a water tank and not sure which is going to be the best investment? One thing about water tanks is that just because you buy a cheaper steel tank, doesn’t mean you’re getting a better deal. Not all steel tanks are created equal, and the choice you make can significantly impact your long-term costs.

How significant are the cost differences? Some tanks, while cheaper upfront, can end up costing you over 25% more over the life of your tank. To understand why this is and how to make the buying decision that’s right for you, let’s look at how steel tanks are made and the impact of this on corrosion protection.

How Steel Tanks are Made

Steel tanks are a popular choice for water storage due to their strength and durability. Smaller steel tanks are manufactured as a sealed unit, but larger tanks, commonly used for rural and commercial properties, are assembled onsite. Because these tanks are bolted together, the tank shell is not watertight, so a liner is inserted into the tank to hold the water. The shell of these steel tanks is made from either galvanised steel or Zincalume. As we’ll see next, the material used makes a difference to the upfront and ongoing costs.

The Corrosion Challenge

However, the space between the liner and the steel tank can create a corrosion issue, especially when moisture gets trapped in this space.This is where the difference between zincalume and galvanised tank shells comes into play. For Zincalume tanks, this trapped moisture can lead to corrosion if not suitably offset via the use of a sacrificial anode (more on this soon). However, Galvanised tanks are naturally protected against this threat.

Addressing the Corrosion Issue

To address this corrosion issue, different strategies are used for Zincalume and galvanised steel tanks.

Zincalume Tanks and Sacrificial Anodes

1. Use of Sacrificial Anodes: ZINCALUME® tanks are coated with a mix of zinc, aluminium, and magnesium. To protect these tanks from corrosion in constantly moist environments, sacrificial anodes are used. These anodes are designed to corrode instead of the tank, thereby protecting the tank itself.

2.How They Work: Sacrificial anodes are made from materials that corrode more easily than the Zincalume coating. When operating properly, they attract corrosion, sparing the steel tank.

3.Maintenance Needs: Sacrificial anodes need regular replacement, typically every few years, depending on the environment and usage. This ongoing maintenance adds to the overall cost and effort required to keep Zincalume tanks in good condition.

Challenges of Sacrificial Anodes

While sacrificial anodes are effective in theory, their actual functional effectiveness can be limited. On land, their conductivity is not as high as other environments where their application is more robust, such as in boats that go on sea water, making them less efficient. Additionally, if not replaced on time, the tank becomes vulnerable to corrosion, leading to potential damage and costly repairs.

Galvanised Steel as the Alternative Solution

Galvanised steel tanks offer a different approach to combating corrosion. These tanks are coated with a thick layer of zinc, which provides robust protection.

1. Maintenance-Free Protection: Unlike Zincalume tanks, galvanised steel tanks do not require sacrificial anodes. The zinc coating itself acts as a sacrificial layer, corroding before the steel does. This means the steel remains protected without the need for additional maintenance.

2.Durability: The Z450 galvanised coating used by Puraflo is particularly robust, with a thickness of 442g/m², providing excellent protection against rust and ensuring long-term durability.

3. Cost-Effective in the Long Run: While galvanised steel tanks may be more expensive initially, their low maintenance needs and long-lasting protection make them significantly more cost-effective over time.

Looking at the full picture on tank costs

Some people choose Zincalume tanks because they believe them to be the cheaper option. And yes, while you typically save around 10% upfront on a Zincalume tank versus a galvanised tank of the same size, the long-term cost becomes higher due to the need for periodic anode replacement.

Galvanised Steel vs Zincalume: Which is Better for Water Tanks?

The following comparison shows the strengths and weaknesses of materials used in steel water tanks.

Feature	Galvanised Steel	Zincalume
Feature Initial Cost	Galvanised Steel Higher	Zincalume Lower
Feature Lifetime ownership Cost	Galvanised Steel Lower	Zincalume Higher
Feature Maintenance	Galvanised Steel Minimal	Zincalume Requires regular sacrificial anode replacement
Feature Durability	Galvanised Steel High	Zincalume Moderate
Feature Protection Mechanism	Galvanised Steel Thick zinc coating which provides no-cost corrosion protection	Zincalume Combination of zinc, aluminium, and magnesium with sacrificial anodes
Feature Best for	Galvanised Steel Constant moisture, limited airflow like the inside of your water tank	Zincalume Applications with good airflow like roofs, cladding.

Lifetime ownership cost comparison: Galvanised vs Zincalume tank shells

Image: Example Tank Cost over 20 Years – Source: Aquamate

Why pay to maintain your tank warranty?

When considering a tank’s warranty, it’s important to understand the maintenance requirements attached to it. For Zincalume tanks, replacing sacrificial anodes is typically a condition of the tank warranty. This means regular maintenance is necessary to keep the warranty valid. Failure to replace these anodes as strictly given by the warranty provider, can void the warranty, removing the added protection of your tank when you may need it most.

In contrast, galvanised steel tanks, such as those from Aquamate, come with a 20-year pro-rata warranty that requires no service costs. This ‘no service costs’ warranty means you don’t have to worry about regular maintenance or additional expenses to keep your tank protected for the long term.

Galvanised vs Zincalume Tanks - What’s most cost-effective?

When considering a steel tank, it’s best to take into account both the upfront and ongoing maintenance costs.

Ultimately, the choice is to either save a little upfront with a Zincalume tank or save more over the life of the tank with a galvanised steel tank.

At Puraflo, our goal is to provide you with the perfect water storage solution for your property. Contact us today or give us a call for a quick quote or personalised advice about our high-quality galvanised steel tanks..

1300 650 672