Which is better: stainless steel or galvanised steel?
As plain carbon steel rusts easily in most environments if left unprotected, there are many ways to modify steel to prevent corrosion. Two popular solutions are stainless steel and galvanised steel. While both steels are resistant to rust and corrosion, there are some important differences between them that need to be understood.
In the following Tisco Steel article we will tell you more about them and which of the two will be best for your steel product.
How is stainless steel created?
Stainless steel is resistant to corrosion due to the additional alloying elements in its chemical composition. Whereas ordinary carbon steel consists mainly of iron and carbon, stainless steel has a large amount of chromium added to help it resist corrosion.
Chromium, and sometimes other alloying elements, are added to stainless steel during the initial melting process, before it is given a specific shape.
So, what is galvanised steel?
Galvanised steel is a type of steel that has been coated with a layer of zinc to help prevent the underlying steel from rusting. This layer is usually quite thin, usually measured in thousandths of an inch or micron.
To manufacture galvanised steel, the zinc layer is usually added well after the steel sheet or plate has been cast, refined and formed. Sometimes it is even applied after the fabrication process on it, such as bending or welding, has been completed.
How does stainless steel resist corrosion?
Which is better, stainless steel or galvanised steel?
Thanks to the addition of chromium (and sometimes other additional elements), stainless steel is resistant to corrosion. In the case of carbon steel, corrosion occurs when the iron in the steel is allowed to combine with the oxygen in the surrounding environment.
In contrast, the chromium in stainless steel is able to prevent this by combining with oxygen and forming a passive chromium oxide layer. In many cases, this layer prevents the formation of iron oxide provided the chromium content of the steel is sufficiently high.
The different grades of stainless steel specify and determine the amount of chromium and other alloying elements required, which helps to indicate the level of corrosion resistance of this metal.
So how does galvanised steel resist corrosion?
Galvanised steel resists corrosion because it has a zinc coating on it. This coating serves two purposes.
It prevents oxygen from coming into contact with the steel, thus reducing the likelihood of corrosion.
Even if the zinc coating is slightly damaged and a small amount of iron is exposed to the atmosphere, the nearby zinc is more reactive than the steel in the rest of the coating. This allows zinc to attract oxygen molecules more readily than iron, thus preventing rust from forming on the steel.
Stainless steel or galvanised steel?
Stainless steel usually has better corrosion resistance than galvanised steel. If stainless steel is scratched, it will still retain its resistance to corrosion in the affected area. However, if the zinc layer of galvanised steel is damaged, it leaves the carbon steel beneath exposed and vulnerable.
As galvanised steel is usually extensively zinc dipped and then cut to size, the cut edges are exposed, increasing the chances of rusting over time.
Stainless steel is also often considered more aesthetically pleasing than galvanised steel as it usually has a bright silver colour, whereas galvanised steel has a dull grey pattern. However, stainless steel is also usually more expensive than galvanised steel.
Applications of these two types of steel
Which is better, stainless steel or galvanised steel?
Stainless steel is often used in applications where the risk of corrosion is a major concern and requires avoidance at all costs. Areas of use for stainless steel include.
Food processing equipment
Pharmaceutical production equipment
Aerospace engine components
Kitchen appliances
Certain types of fasteners
Applications of galvanised steel
In contrast, galvanised steel is used in applications where corrosion is not desirable, but where a small amount of corrosion can be allowed and where aesthetics are not a major concern. Common applications include.