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Difference Between Stainless Steel and Galvanised Steel

If left unprotected, ordinary carbon steel remains susceptible to rust in most environments. For this reason, there are many ways to modify steel to prevent corrosion. Two popular solutions are the use of stainless steel or galvanized steel. While both types of steel protect against rust and corrosion, there are some important differences between them that should be understood.

What is Stainless Steel?

It is resistant to corrosion because of the additional alloying elements in its chemical composition. While ordinary carbon steel is composed primarily of iron and carbon, it has a significant amount of chromium added to help it resist corrosion. Chromium, and sometimes other alloying elements, are added to it during the initial melting process, before it is formed into any particular shape.

Difference Between Stainless Steel and Galvanised Steel

What is Galvanised Steel?

Galvanised steel is a type of steel that is coated with a layer of zinc that helps prevent the underlying steel from rusting. The layer is usually very thin, usually measured in thousandths of an inch or micron. To create galvanised steel, the zinc layer is usually added after the steel sheet or plate has been melted, refined and formed. Sometimes it is even applied after a fabrication process (such as bending or welding) has been performed on it.

How Does Stainless Steel Resist Corrosion?

  1. Thanks to the addition of chromium (and sometimes other additional elements), stainless steel resists corrosion. Carbon steel corrodes when the iron in it is allowed to combine with the oxygen in the surrounding environment. The chromium in it prevents this because it combines with oxygen and forms a passive layer of chromium oxide.
  2. This layer of chromium oxide prevents the formation of iron oxide, (also known as rust), in many cases, provided the chromium content of the steel is sufficiently large. The different grades of stainless steel specify and determine the amount of chromium and other alloying elements required, which helps indicate the level of corrosion resistance.
Difference Between Stainless Steel and Galvanised Steel

How Does Galvanised Steel Resist Corrosion

Galvanised steel resists corrosion because of the zinc coating covering the carbon steel. The zinc layer serves two purposes:

  1. It prevents oxygen from coming into contact with the steel, thus reducing the possibility of corrosion.
  2. Even if the zinc coating shows slight damage and exposes a small amount of iron to the atmosphere, the zinc near the rest of the coating is more reactive than steel. This allows zinc to attract oxygen molecules more readily than iron, thus preventing rust from forming on the steel.
Difference Between Stainless Steel and Galvanised Steel

The Difference Between Stainless Steel and Galvanised Steel

  1. Stainless steel typically has better corrosion resistance than galvanized steel. If stainless steel is scratched, it can still maintain corrosion resistance around the affected area. However, if the zinc layer of galvanized steel is damaged, it leaves the underlying carbon steel exposed and vulnerable. Also, because galvanized steel is usually zinc dipped in a large sheet and then cut to size, the cut edges are exposed, leaving it open to rusting.
  2. Stainless steel is also often considered more aesthetically pleasing than galvanized steel because stainless steel usually has a shiny, silver-like color, while galvanized steel has a dull gray pattern. However, stainless steel is also usually more expensive than galvanized steel.

Applications of Stainless Steel

Stainless steel is typically used in applications where the risk of corrosion is high and not permitted. Areas of use for stainless steel include:

    • Food processing equipment
    • Pharmaceutical manufacturing equipment
    • Aerospace engine components
    • Kitchen appliances
    • Certain types of fasteners

Applications of Galvanised Steel

Galvanized steel is used in applications where corrosion is not desired, but where a small amount of corrosion may be allowed and there is not much aesthetic impact. Applications for galvanized steel include:

  • Duct work
  • Automotive components
  • Some types of fasteners
  • Structural beams
  • Metal cabinetry
  • Railing
  • Walkways
  • Traffic signs
  • Electric poles
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