Difference Between Stainless Steel and Galvanised Steel

Steel comes in various forms and types. It is highly versatile and modified to keep up with the various environments and requirements of the different applications. The two most popular types of steel are stainless and galvanised steel. They share multiple similarities, but more importantly, they also have differences that make them better suited for different applications.

What is Stainless Steel?

Stainless steel is an iron and chromium alloy. To be considered stainless, the alloy must contain at least 10.5% chromium, but the exact components and ratios will vary based on the grade requested or the intended use. Stainless steel includes other additives like nickel, carbon, nitrogen sulphur, copper, manganese, molybdenum, and silicon. The types of additives added to determine the qualities the final stainless steel will possess.

What is Galvanised steel?

Galvanised steel is essentially zinc-plated steel. There are multiple ways to galvanise steel, but the results are similar as long as each method is correctly performed. The most common method of galvanising steel is hot-dipping. In this process, standard steel is dipped in molten zinc, creating a layer of zinc that bonds with the surface of the steel to provide protective benefits and an appealing appearance.

Other methods of galvanising steel include electro-dipping and thermal diffusion. The additional zinc layer helps the metal resist corrosion, dings, scuffs and other minor physical abuses.

Corrosion Resistance

Stainless steel is best known for its corrosion resistance properties. Adding a zinc layer on galvanised steel also gives the final product some corrosion resistance properties but is not nearly as effective as those of stainless steel.

Galvanised steel offers excellent corrosion resistance against water and chlorine but is not as impressive as stainless steel in marine environments. Also, the protective layer on galvanised steel is not self-healing like that of stainless steel.

Overall, stainless steel offers better corrosion resistance over a longer period and broader applications.

Strength

Both types of steel have steel as the primary component. But when compared in similar thicknesses and forms, stainless steel always emerges as the stronger metal.

You can compare the strength of each material by looking at its tensile strengths. The exact figures vary depending on the alloy. Typically, for stainless steel alloys, tensile strength begins at 515MPa and can reach as high as 1300MPa.

Structural steel has a minimum of 400MPa, while carbon steel has a minimum tensile strength of 841MPa. Both are used to create galvanised steel.

Galvanising steel doesn’t impact the tensile strength of the underlying metal, so you can expect galvanised steel to have comparable tensile strength to the original steel.

Weight

Weight is a substantial factor to consider when choosing a material. In most cases, stainless steel and galvanised steel have the same weight. But the specific weight difference will vary depending on the exact stainless steel alloys in question and the zinc coating thickness on the galvanised steel product.

Metals with a thicker zinc coating will result in greater weight. But with all factors constant, both materials have relatively the same weight.

Malleability

Galvanised steel offers the same malleability as the underlying steel used. In most cases, galvanised steel will be more malleable than comparably shaped stainless steel forms. If you have to use stainless steel and want greater malleability, you can use austenitic grades, which have a higher amount of nickel, making them more formable for larger objects like sinks, basins and tanks.

Weldability

Both galvanised and stainless steel are weldable, although with unique considerations. Welding stainless steel can degrade the passive layer and creates brittleness. This reduces corrosion resistance or compromises the structural integrity of the stainless steel parts.

Pickling treatments can help to reduce the impact of the weld and heat exposure in most stainless steel applications.

With galvanised steel, you must adequately capture or ventilate the welding fumes as zinc oxide fumes can be harmful when inhaled.

If welding near stainless steel, you must keep the molten zinc away from the stainless steel components, which could create embrittlement of the affected stainless steel. For this reason, you should perform welding before galvanising where possible.

Magnetism

This answer depends wholly on the family of steel used. The zinc layer won't interfere with the magnetic response for galvanised steel, where the steel used was magnetic. If you prefer to avoid magnetic options as per the requirements of the application, avoid austenitic steels because they are the most magnetic. Other alloys exhibit various levels of magnetism based on their iron content.

Uses

Stainless steel is preferred for its durability, easy cleaning, maintenance and versatility. Its range of applications includes:

Galvanised steel is often viewed as an affordable alternative to stainless steel. It has regular applications in various industries, including: