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Metal Roof Protection: What Are the Coating Technologies?

26 October 2020

If you have an industrial or commercial metal roof and are trying to decide what is the best option in protective coatings for it, then this blog is for you. Whether you are working on dilapidations of an already rusty roof that needs a stronger protective roof coating, or carrying out planned maintenance, read on to see what is available on the market for you.

Silicone Coatings

Silicone coatings are often specified for metal roofs as they have good overall elasticity and weatherability as well as are good at withstanding thermal differences. They also dry off quite quickly when it has been raining. However, there are some downfalls of silicone coatings.

When applying silicone coatings, they are extremely averse to being applied in damp conditions. Having a very low damp tolerance means they have to be applied on completely dry metal substrates, and this can cause an issue for working schedules, slowing jobs down.

Silicones negative environmental implications are that they contain volatile organic compounds (VOCs). VOCs are found in solvents which are used in many paints and coatings to make them easy to apply and spray. These chemicals are toxic and pollute the air, contributing to ground-level ozone that is harmful to animals and humans.

Furthermore, as silicone coatings contain VOCs, as the vapours are released in the atmosphere the coating will shrink on curing which means the appearance and thickness will reduce during curing. This is also compounded by silicone coatings’ is their low tensile strength which means the coating is vulnerable on parts of the roof such as the edges and gutters where maintenance might occur. The softness of the coating can then, therefore, leave weaknesses for moisture to get in and corrosion to occur.

Polyurethanes

Polyurethanes have a higher impact resistance than silicone coatings, therefore, can stay cleaner for longer. They also have a good tensile strength so none of that weakness at the gutters as mentioned above.

However, one of the main drawbacks to polyurethane coatings is that they usually contain a lot of solvents and always contain isocyanates, which is an extremely toxic vapour linked with asthma and chemical burns. Other issues with its application are that there is a limited time to recoat. This means, for example, the 2nd coat isn’t applied in time, you will have to start from the beginning, priming and coating it all over again.

Polyurethane coatings are also known for their extremely heavy film weight with 1.5-2kg of coating needed per square meter. This means that for many medium-sized roof jobs (eg around 4000m2) you could see around 8 tonnes of roof coating used. The environmental impact of that is enormous, especially when alternate roof coatings, such as Advantage Graphene would see the same job using a 1/10th of that.

Even more significant is the aspect that as polyurethane coatings often contain around 15% solvents, then around a tonne of solvents would be released into the environment from that one job, not to mention the carbon footprint and waste from packaging and raw materials from the 530 tins of topcoat used. Furthering from the previous example of the reduction in waste that using Advantage Graphene would have done for that job, is that you would only need 53 tins. Just one job would see you saving the waste of packaging and tins from 477 tins!

Acrylics, Alkyds, Vinyls and Other Older Coating Technologies

For many people, when choosing a roof coating, they will just look at the price and spread rate in order to make their decision and go with a cheap acrylic or vinyl coating, but they fail to realise the other aspects of these coatings. For example, they are often multicoat systems which therefore requires more product, and they are shockingly only around 35-65% solids, meaning on some coatings up to 2/3rds of the contents are going into the environment and not staying on your roof.

Due to the low solid content, these coatings also shrink on curing so require multiple coats and can become brittle and weak over time. This is compounded by their poor weatherability which means these coatings overall have a shorter life expectancy.

Hybrid Coatings

Hybrid coatings combine the better properties stated above of silicone and polyurethane coatings. They are a big improvement on previous coating technologies for performance, application and the environment.

Some are solvent-free and also moisture tolerant, removing any stress of having to work on a completely moisture-free surface extending the working window of seasonal applications. Hybrid coatings also have high elasticity, increasing their toughness.

There is one hybrid coating that is leading the way from an environmental perspective – it contains 100% solids and therefore releases nothing into the environment.

Graphene Enhanced Hybrid Coatings: Advantage Graphene

At Alltimes Coatings we took our own hybrid and enhanced it with the properties of graphene. By combining the already proven durability and performance of our hybrid coatings with one of the thinnest, but strongest, materials in existence, the coating forms a virtually impenetrable barrier to moisture. This is unlike other coatings on the market which can wear down over time letting in moisture and welcoming rust and corrosion onto metal roofs.

Advantage Graphene’s enhanced life expectancy, which is guaranteed for up to 30 years, comes from the chemical structure of its particles which are in a 2D hexagonal shape. This unique arrangement increases the surface area of the coating and therefore multiplies the distance water particles have to travel to reach the metal substrate at a molecular level.

It is also an extremely environmentally friendly coating as it is solvent, isocyanate and VOC free due to it containing 100% solids and therefore releasing nothing into the environment. This drastically reduces the volume of coating needed for a roofing job, reducing the raw materials, shipping, packaging and carbon footprint of the product.

Graphene enhanced hybrid roof coatings are a familiar application process for applicators as well as completely safe and nontoxic. Also interesting is the fire resistance of the coating with it’s BS EN 13501-5 testing at BRE.

Conclusion

According to data from the Financial Times, corrosion in its many forms is estimated to cost the global economy $3 trillion a year due to damage to steel buildings and infrastructure. That’s why it is so important to put in measures of prevention through effective and long-lasting coating systems. Implementing a coating solution with an almost impenetrable barrier to corrosion will reduce the long-term impacts rust has on your roof projects.

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. But that’s just what we think… 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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