Steel Rust

Steel is a robust, resilient and durable material which can main its structural integrity for decades if it is not exposed to corrosion.

1. Introduction

All steel materials, including steel structures, are susceptible to rust. If steel is not protected, rust is mostly unavoidable therefore all steel fabrications are subject to coating for a long lifetime. This article will present techniques and methods on how to avoid corrosion on steel structures.

2. What is rust?

Rust is the term used to describe red iron oxides produced when ferrous metals corrode. Rust is the common name for the chemicals that result when iron reacts with oxygen and water. “Rust” is poorly defined in chemistry, however—lots of chemicals can be formed when iron is left exposed.

Figure 1: Rusty Steel

3. What causes rust?

Any material made with iron that is exposed to both oxygen and water will rust. Because steel is made almost entirely of iron, it is the most highly manufactured man made material that is subject to rust.

While steel buildings and beams are structurally sound and stable, water molecules can penetrate those microscopic, near-invisible gaps within the steel. Once they creep within the metal, it starts to corrode slowly. Where salt is present – in seawater, for example – the corrosion process will be quicker. The presence of salt acts as a catalyst, accelerating the corrosion chemical reaction process

4. Types of Coatings
  • Galvanising

Hot dip galvanization is an excellent solution for preventing rust. The steel product is coated in a zinc layer, which acts as a protective barrier for the metal underneath, against oxygen and water. Zinc is more reactive than iron, so the zinc oxidises, rather than the metal itself.

Figure 2: Hot Dip Galvanization

  • Painting

Protective painting systems usually consist of primer, intermediate/build coats and finish coats. Each coating ‘layer’ in any protective system has a specific function, and the different types are applied in a particular sequence of primer followed by intermediate/build coats in the shop, and finally the finish coat (or top coat) either in the shop or on site. There are various steel structure paint types to be considered based on the

Figure 3: Steel Painting

  • Powder coating

Powder coating involves adding dry powders to clean surfaces, heating the object and subsequently turning the powder into a thin film. This film adds another layer of protection for structural steel surfaces against corrosion.

Figure 4: Powder Coating

5. Conclusion

The coating type of each steel structure should be decided based on the below criteria;

  • What kind of painting conditions are we working with?
  • What kind of environment is our end product used in? (Is it indoors? Or are there harsh weather conditions?)
  • What types of metal surfaces are we working with?
  • How long do we want the paint to hold?

For all the coating methods, a proper surface preparation is essential prior to the commencement of coating.

As with any field or industry, there are certain standards and regulations that need to be taken into account when deciding which product to go with. Novelty Steel complies with ISO 12944 International corrosion protection standard in its products.

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