Material Differences Between Stainless Steel and Galvanised Steel

14 September 2020

Steel is an alloy that is mainly composed of iron and carbon, on which the latter provides the material’s needed improvements over its strength and fracture resistance. This specific alloy is known to be one of the most important engineering and construction material due to the benefits that it possesses. Some of these benefits include high strength, great aesthetic appearance, sustainable, reliable, and cost-effective.

Despite these benefits, plain carbon steel can still rust and corrode easily. So, to solve the issue of corrosion, this specific alloy is further modified into different grades and types. Two of the most popular modifications for plain carbon steel are stainless steel and galvanised steel.

Stainless Steel

Stainless steel is an alloy of iron and carbon that is combined with a minimum of 10.5% chromium. The integration of chromium allows this alloy to obtain a thin passive layer of chromium oxide that can prevent the surface from corroding and deteriorating. Increasing the chromium percentage of stainless steel makes the alloy more resistant to corrosion. Some other elements that can be combined with stainless steel are nickel, molybdenum, silicon, and manganese.

As mentioned, stainless steel becomes more resistant to corrosion due to the presence of chromium. This element, which was mostly added during the initial melting process, seamlessly combines with the oxygen for it to form a passive layer of chromium oxide. This specific layer deters the formation of rust or iron oxide and protects the surface from deterioration. The amount of chromium that is present on a specific grade of stainless steel determines its respective corrosion resistance.

Applications that are exposed to corrosive elements can benefit the properties of stainless steel. Some products that are made from stainless steel include food processing equipment, aerospace engine components, kitchen appliances, fasteners, and pharmaceutical manufacturing equipment.

Galvanised Steel

Galvanised steel is a type of steel that is coated in a zinc layer, which hugely offers surface protection and prevents the underlying steel from corroding. The layer of zinc is added after melting, refining, or shaping the steel plate or sheet. This layer acts as a protective barrier for the galvanised steel, making it possible for products fabricated from this material to last for a very long time.

The zinc coating of galvanised steel has two main functions. For one, it prevents the oxygen element from infiltrating the steel surface. Without oxygen, the possibility of corrosion will be minimised. Another function of zinc coating is it sacrifices itself to any corrosive element that is present in the surroundings. The coating may get damaged in the long run, but other parts of the coating will still shield the underlying surface from corrosion by attracting the oxygen into the coating, leaving the iron elements alone.

Applications that have small amounts of corrosion can utilise materials made from galvanised steel. Some of the products that can be made from galvanised steel include ductwork, automotive components, structural beams, railing, walkways, traffic signs, electric poles, and metal cabinetry.

Comparing Steels

When it comes to corrosion-resistance, stainless steel is believed to be better compared to galvanised steel. Stainless steel can easily maintain its corrosion resistance despite getting some scratches. Galvanised steel, on the other hand, may get exposed to corrosion once its zinc layer gets damaged. The appearance of stainless steel is also much better than galvanised steel since the former has a shiny, silver colour compared to the dull-grey pattern of the latter. One great thing about galvanised steel, though, is it costs cheaper than the stainless steel.

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