Stainless steel vs. galvanised steel

Stainless steel and galvanised steel are both commonly used materials in construction. While they are similar in appearance they differ in terms of composition, weight, strength and application, although there is a certain amount of crossover between them.

Stainless steel is manufactured by a process that involves a mixture of at least 10% chromium and regular carbon steel in a molten state. Once it is cooled and hardened, the steel is acid-treated to remove any impurities from the surface. It is the addition of chromium that protects stainless steel from corrosion.

Galvanised steel is manufactured by a process that involves dipping steel into molten zinc which hardens to form a protective, anti-corrosive coating through the formation of zinc oxide.

The zinc coating on galvanised steel eventually wears off, and if is scratched or damaged in any way, it can become susceptible to rust. However, The zinc acts as a sacrificial anode, meaning that the remaining zinc will still protect the exposed steel.

It's use is typically restricted to applications where there is minimal risk of damage. Galvanised steel is significantly less expensive than stainless steel, and is commonly used, for example, to make; nuts, bolts, fasteners and other fixings (although some components may be too large or too small to be hot-dipped), as well as being used in many common appliances.

For more information see: Galvanised steel.

In contrast, stainless steel retains its anti-corrosive qualities for longer, as the chromium forms an inextricable part of the steel material itself. As a result, stainless steel is more durable than galvanised steel, and is preferred for some uses in the construction of buildings, such as the construction of high-rise buildings. It does not rust even when scratched, so is commonly used for the working parts of hand tools such as saw blades. It is also more resistant to salt than zinc oxide, and so is more commonly used for applications in marine and coastal environments.

For more information see: Stainless steel.

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• Concrete vs. steel.
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• Major cast metal components.
• Metal fabrication.
• Rebar.
• Rust.
• Stainless steel.
• Structural steelwork.
• Weathering steel.