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What’s the Difference between Galvanised Steel and Stainless Steel?

Published by Lucy Thurston on

What's the Difference between Galvanised Steel and Stainless Steel?

As galvanised steel sheet suppliers in the UK, we’re often posed the question of what the difference between galvanised steel and stainless steel is. The property that links galvanised steel sheet metal to stainless steel is that they both effectively resist corrosion. Despite this, from the galvanised steel sheet thickness to the strength, there are many factors that set galvanised steel apart from stainless steel.

Steel itself is a metal alloy that’s composed of iron and various other elements. The material is widely applied on a global scale due to its notable strength, simple production, and minimal cost. Read on to discover more about the differences between galvanised steel and stainless steel.

What’s Galvanised Steel?

Galvanised steel is essentially steel that’s been coated in molten zinc, a process that’s otherwise known as galvanisation, to shield it from rusting. There are a couple of methods of achieving this; however, the most common is known as hot-dip galvanising. This refers to the process in which a steel product is submerged in a molten zinc bath. As a result, the steel underneath is protected from rusting, thanks to the layer of zinc. Even if a small area of the coating is damaged, the zinc will act as an anode and shield the exposed area from rusting. This means that the zinc is oxidised, as opposed to the steel. Despite this, the coating is only around one millimetre thick, meaning a large scratch will result in the rusting of the steel.

Alternatively, steel may be galvanised via the process of electro-galvanising, which refers to the steel being submerged into an electrolyte solution containing a zinc electrode. With this being said, galvanised steel isn’t the strongest of metals; however, it is affordable.

What’s Stainless Steel?

Stainless steel is made via the combination of molten steel and molten chromium, wherein at least 10% of the metal alloy will be chromium. This combination of metals allows for increased strength; however, the production is relatively expensive. It’s imperative that both metals are molten during the mixing stage; otherwise, the uniformity of the mixing won’t be achieved. Following this combination, the steel is cooled and hardened, before the surface is washed with acid to strip the metal of impurity.

Unlike galvanised steel, even if stainless steel is scratched, rusting won’t occur. This is because chromium is present throughout the metal, not just on the surface. Consequently, stainless steel is resistant to air and even some acids.

The Difference Between Galvanised Steel and Stainless Steel

To summarise, galvanised steel is created by submerging steel in molten zinc, whilst stainless steel is crafted by combining molten steel and molten chromium. Galvanised steel is merely coated, whilst stainless steel refers to the composition of the alloy being completely altered.

What's the Difference between Galvanised Steel and Stainless Steel?

How Does Galvanised Steel Resist Corrosion?

Corrosion occurs on steel in the instance that the iron from the steel is able to come into contact with the oxygen in the atmosphere. This results in the formation of iron oxide, which is more commonly known as rust. Therefore, the zinc coating that’s applied via the galvanisation process prevents oxygen from reaching the steel, which minimises the likelihood of corrosion.

How Does Stainless Steel Resist Corrosion?

Since chromium is more reactive than iron, the chromium content of the stainless steel will attract the oxygen molecules over the iron. Consequently, a passive layer of chromium oxide is created, which inhibits the production of iron oxide. It’s for this reason that stainless steel is more resistant to corrosion than its galvanised counterpart.

Cost

As previously mentioned, the galvanised steel sheet cost is lower than the cost of stainless steel. For instance, our 1.2mm mild steel galvanised sheet costs £52.80 +VAT per square metre, whilst our 1.2mm stainless steel (304) dp sheet will set you back £133.90 +VAT per metre squared.

Strength

When compared to stainless steel, galvanised steel isn’t very strong at all. Steel is the second strongest metal on earth and by incorporating the right elements, this strength is only heightened.

Weight

Despite the fact that stainless steel is considerably stronger than galvanised steel, the weight of the two isn’t too dissimilar. Stainless and galvanised steel sheet cut to equal sizes will have a relatively similar weight, depending on the thickness of the coating and the stainless steel alloys. After all, a thicker coating or more alloyed metals will lead to an increased weight.

Malleability

In most cases, galvanised steel is more malleable than stainless steel, as galvanised steel offers the same malleability as the underlying steel. Despite this, if your project requires stainless steel and you require enhanced malleability, solutions with higher amounts of nickel would be the most appropriate choice.

Conduction

As far as conduction is concerned, galvanised steel and stainless steel operate in a somewhat similar way. Despite this, when it comes to galvanised steel, the melting temperature of zinc must be considered. This is because heating galvanised steel beyond zinc’s melting point may lead to burn or fire hazards. With this being said, both types of steel are suitable for use in high-heat areas.

Weldability

Both types of metal can be welded; however, each presents individual complications. For instance, welding galvanised steel produces zinc oxide fumes, which are harmful when inhaled, meaning necessary ventilation must be put in place. On the other hand, welding stainless steel can result in brittleness and the degradation of the passive layer. Consequently, the structural integrity and corrosion resistance can be compromised.

Magnetism

The magnetism of each type of steel depends on the steel family used. As far as galvanised steel is concerned, the coating shouldn’t affect the magnetic response of the steel. Alternatively, the composition of stainless steel can be customised to make it either more or less magnetic.

Buy Stainless and Galvanised Steel Sheets from Rapid Metals

Regardless of which type of steel is required, we’ve got you covered. Browse our collection of stainless sheet steel and galvanised steel sheet sizes or contact us with any other metal enquiries.

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