When it comes to stainless steel, the first thing that often comes to mind is cutlery, cookware, or other kitchen accessories. Meanwhile, galvanized steel is commonly associated with construction, which has been used since the nineteenth century as a relatively inexpensive material. Yet these two types of steel have specific properties that make each one useful for particular purposes. Let’s look at some differences between stainless steel vs galvanized steel, and each of their many applications.
Each type of steel is formed differently. First, steelmakers heat coal until it’s basically carbon or coke, and then leave it to cool. To make steel, the iron ore is heated and melted to remove impurities, with coke then added to provide greater strength. Most steel is made with either blast furnaces or electric arc furnaces. The former mainly use raw materials – generally iron ore, coke, and limestone – whereas the latter mainly uses scrap steel.
Making galvanized steel involves coating it with a thin layer of zinc, in a process called hot-dip galvanizing. It involves immersing steel into molten zinc to create a multi-layered coating of zinc and iron alloy that helps the metal resist corrosion. Welders working with galvanized steel require protection against its fumes, as zinc’s boiling point is below that of the steel, and welding causes zinc to vaporize.
Stainless steel involves a more complex process, with chromium, silicon, nickel, carbon, nitrogen, and manganese added to molten steel. It’s then cast into semi-finished forms before being heated again and reformed into sheets, bars, wires, plates, and strips. Most types of stainless steel also go through annealing, a controlled treatment where the steel is heated and cooled to soften the metal and relieve internal stresses. When it comes to welding, welders need to take more care when heating and cooling stainless steel, matching filler materials with those being welded.
Generally, the more complex the alloy, the greater the strength. While galvanized steel is more supple and easier to work, stainless steel resists corrosion better and is stronger.
The zinc that coats galvanized steel protects it from rust by keeping the steel from coming into contact with oxygen, which causes corrosion. This keeps nails, bolts, nuts, and screws from degrading when exposed to the weather. Even when this zinc coating receives minor scratches, it still resists corrosion due to the fact the surrounding zinc is more reactive than steel, preventing rust from forming.
It’s even water-resistant, though tends to corrode faster than stainless steel when exposed to seawater. The combination of salt, moisture, and oxygen causes metals to corrode, with saltwater causing corrosion five times quicker and seawater accelerating it to 10 times, as it also contains bacteria that consume the iron. The temperature of seawater also affects its degradation, with tropical seawater causing galvanized steel to corrode even more quickly than seawater at lower temperatures.
Elements in stainless steel – especially chromium – allow it to resist corrosion much better. The chromium combines with oxygen in the environment to create a passive layer of chromium oxide, which helps prevents iron oxide from forming. Grades of stainless steel with higher amounts of chromium better resist rusting and, like galvanized steel, scratches can still resist corrosion around affected areas.
The zinc layer surrounding galvanized steel tends to be less effective against corrosion, especially when exposed to seawater, which is why stainless steel is used for sea-going vessels and other environments in which metal is exposed to saltwater. Additionally, many people consider stainless steel the more attractive option. Considering its shiny, silvery color compared to the dullish gray of galvanized steel, stainless steel offers a better aesthetic look.
When considering stainless steel vs galvanized steel, it’s especially important to consider for what purpose the metal will be used. Both metals have certain advantages and disadvantages.
Many vehicle bodies and bicycles are often made from galvanized steel, as are water pipes for drinking water, nuts and bolts, tools, ladders, wiring, and rolled sheet metal, as galvanized steel is less expensive yet extends the lifecycle of metal parts in products. It’s also used in steel frame construction, including skyscrapers, roofing, balconies, verandas, and staircases.
Galvanized steel tends to be used when aesthetics or corrosion are less of a concern, such as for:
- Air ducts
- Automobile components
- Certain fastening implements
- Electrical poles
- Metal cabinets and other furnishings
- Outdoor walkways
- Structural supports
- Traffic signs
Stainless steel is equally versatile and comes in many varieties. Machine shops often use austenitic stainless steel, while automobile exhaust pipes tend to be made from a less expensive type called ferritic stainless steel. Martensitic stainless steel is hardened and tempered, used mainly in medical instruments such as razors, scalpels, and internal clamps. Combining the molecular structure of ferritic and austenitic stainless steel, duplex stainless steel is used for industrial purposes that include oil and gas exploration, cooling pipes, paper manufacturing, mechanical components, marine environments, and chemical processing. Often containing rare metals like niobium, precipitation hardening stainless steels have incredibly high tensile strength and are used in the nuclear and aerospace industries.
Typically used where corrosion is a real risk, stainless steel is used in:
- Engine components for spacecraft
- Food processing
- Kitchen appliances
- Pharmaceutical industry
- Some fastening implements
As stainless steel is the more complex alloy, it costs significantly more, and also tends to be more expensive to work. Additionally, because it’s a prettier metal, stainless steel is more sought after in higher-end and artistically designed metal products. While galvanized steel costs about as much as untreated structural steel, stainless steel costs as much as five times this price, with certain allows being even more expensive.
Choosing Between Stainless Steel vs Galvanized Steel
There are many factors to consider when making the choice between stainless and galvanized steel, ultimately depending on what its purpose or application will be.
At Atlantic Stainless, we can assist you in determining what material ideally suits your needs. Even if you’re in the market for a more difficult item, contact us today and let us help you get your project started!