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Galvanised Steel

Galvanised steel is a popular choice in industrial, agricultural, and construction projects. The main purpose of galvanisation is to protect the steel from corrosion, and this is achieved by applying a thin layer of zinc, either through a process of ‘hot dip’ galvanising, electro-galvanising, or metal spraying.

There are a lot of reasons why you should choose galvanised steel for your engineering project. And there are a few more reasons why you shouldn’t. Now knowing what galvanised steel sheet properties are, we have highlighted the key benefits and drawbacks that will guide you to making the right choice for your project.


Durability and longevity

TFM – or Time to First Maintenance – is calculated according to the appearance of rust on five percent of the galvanised steel sheet surface. What this means is that five percent of the zinc coating has now eroded, exposing the steel to corrosion. It is at this stage that maintenance needs to be implemented to protect the integrity of the steel and prolong its durability.

TFM varies according to the atmospheric conditions of the structure. For example, in a dry, rural area with little rainfall and pollution, a TFM could be over 100 years, while in a more humid tropical environment, that TFM might reduce to about 70 years.

By hot-dip galvanising a thin 6mm steel sheet, you are creating a zinc coating of 85 microns, which more than meets the corrosion performance required for many applications across the UK.

Smooth finish, rust-free, and lowered maintenance costs

A sheet of galvanised steel is smooth to the touch, making it easy to inspect. Being tough and durable, it is resistant to scratches and everyday damage. Any damage tends to occur through mishandling and untreated long-term wear and tear. Due to its smooth surface, should the galvanised steel sheet incur any damage, the integrity of the protection is compromised, making it prone to rusting. Fortunately, this makes it easily noticeable on regular inspection and therefore can be treated quickly and effectively. When it is damaged, it is the zinc that is in the first line of fire. That means that the steel underneath is protected and will only be affected if the blemish is left untreated.

Protection from contamination

The galvanisation process acts as a protective buffer against oxygen and moisture, resulting in a smooth, rust-free layer. As a result, the steel sheets are perfect for use in projects which require a clean, clinical environment, such as operating rooms and food preparation areas.


Comparison of steel prices

Galvanised steel sheet prices may be prohibitive, particularly in large-scale projects. Compared with, for example, cold-rolled steel sheet, galvanised steel is considerably more expensive.

When pricing up a project, you need to consider its durability of the project. For a short-term project, which may be demolished in a short period of time, it would be more economical to use a less durable, but better-priced, alternative. However, for long-term structural projects, the additional costs will more than pay for themselves in terms of longevity and reduction in maintenance over the years. Cheaper is never normally better.

Beware of white rust

The galvanisation process ensures that the steel sheet remains resistant to rust. However, you need to be aware of the presence of white rust, which can develop over time if the steel is exposed to moisture and not maintained.

White rust is a white chalky substance that can form on the surface of zinc due to moisture. It can cause significant damage to the galvanised coating and can ultimately compromise the durability of the zinc coating.

Otherwise known as zinc hydroxide, this white rust must be treated immediately to prevent it from spreading and reversing the effect of the galvanisation process as a whole. But prevention is better than cure, so ensure the following steps are taken to minimise the risk of white rust in the first place.

  • Make sure the galvanised steel sheets are packed in a dry, moisture-free environment.
  • Ensure that there is good air circulation between sheets.
  • Store the sheets at a slight angle to ensure that any water or moisture can be drained away and not sit stagnant on the surface of the steel sheets.
  • Make sure the surface of the zinc coating is treated with a barrier or water repellent coating to minimise any contact between water and the galvanised surface of the steel sheet.

If your galvanised steel sheet has developed a white rust coating, then it can be treated. The treatment depends on the severity of the damage to date. If there is a light powdery residue, then it can usually be brushed off with no residual treatment required. However, the more established and severe the zinc oxidisation process, the more remedial treatment is required to ensure it does not compromise the long-term integrity of the galvanised coating.

There are more pros than cons to choosing galvanised steel sheets over alternatives for your construction and infrastructure projects. However, due care and attention need to be paid to the way the steel is stored, handled, and maintained if you are to get optimum return on your investment in the product.

Contact Rapid Metals to discover more about galvanised steel.

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