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Steel Roofs: When Does the Corrosion Start?

23 September 2020

Steel roofs are found on many industrial buildings due to their protective nature, but unfortunately, they are not as long-lasting as we would hope. Steel roofs rust and corrode over time, but when does the corrosion start?

Many steel roofs can have warranties up to 60 years, but they never guarantee a roof won’t rust! That is because all steel roofs can and eventually will. You can see steel roofs with rust in as little as 18 months after installation.

Corrosion and rust can be a nightmare for any building owner, replacing a steel roof can be very expensive too. That is why corrosion treatments and coatings are so important.

Roofing contractor who treats metal roofs call us for corrosion treatments

Steel Sheets Begin Corroding as Soon as They Are Cut

Steel manufacturers seem to think that their factory cut and coated steel sheets are protected from rust, through using zinc alloys and primer. We are here to tell you that unfortunately, avoiding rust on steel sheets is pretty impossible.

In the manufacturing stage, as the metal is cut into sheets, each fresh edge exposes the steel to oxygen and water and begins the process of rust. It’s just a case of time ticking down from that point on. Therefore, roof sheets will always eventually need treatment.

The manufacture of steel sheets goes a bit like this:

  1. The steel is galvanised with a zinc alloy, then primed and top-coated on the weathering side.
  2. The non-weathering side is also coated, but with a thinner and less robust backing coat.
  3. The underside is therefore not very well protected when water gets in.
  4. The metal is cut into sheets and therefore the steel and zinc are exposed from Day 1.

What Does Zinc Alloy Do? (Galvanisation)

The zinc alloy is there to protect the steel, but in a similar process to iron rusting, being exposed to oxygen means it oxidises over time. The zinc alloy slowly turns to iron oxide, which is also known as white rust.

Unfortunately, the zinc oxide doesn’t stick around for long though. Zinc oxide is soluble in water, therefore each time it rains onto the steel roof, the zinc oxide washes away a bit at a time. This is not the end of the world though, as long as there’s enough zinc left. However, on a profile sheet, there was only ever a thin layer there anyway.

Zinc Alloy is designed to be a sacrificial last layer of defence, before the actual metal starts to corrode and crumble. Because neither the original coating nor zinc will last forever, it is necessary to give further protection to metal roof sheets later in their life.

Conclusion: The Solution to Corroding Steel Roofs

Rust affects many metal roofs and can be a tricky and costly issue to face. However, implementing a coating solution with an almost impenetrable barrier to corrosion will reduce the long-term impacts rust has on your roof projects.

Corrosion can seem like something you can’t control, and will eventually occur, but it’s not. You can extend the traditional life of your metal roofs. Our industry-leading graphene-enhanced roof coatings have long-lasting resistance to corrosion. Advantage Graphene has undergone rigorous testing and is approved to ISO:9227.

It can withstand nearly 10,000 hours of harsh corrosion simulation in comparison to the 1,500 hours of testing that coastal coatings are meant to withstand in order to be approved. Advantage Graphene is a metal roof coating with game-changing resistance to corrosion.

Advantage Graphene provides unparalleled protection from rust to all metal surfaces, whilst still being easy and convenient to apply. It is the most advanced and protective roof coating on the market and a huge step forward in innovation in the coatings industry.

Keen to learn more? Check out our latest CPD: Rust Never Sleeps by clicking the link below or call an expert today on 01453 872850.

 

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