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.
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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.
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.
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.
Galvanization is the process of applying a protective zinc coating to steel or iron in order to prevent premature rust and corrosion. Proponents of galvanized steel, who may use it to construct or repair steel structures, for example, benefit from lower maintenance and repair costs because of its special properties.
Galvanization provides corrosion protection, durability under harsh conditions, a long lifespan, versatility, availability, and sustainability. Without protection, steel will rust due to atmospheric conditions over time. The degree of rust will depend on the environment that the product is in. Rust is an iron oxide (typically a red oxide) which is formed by the reduction and oxidation reaction of iron and oxygen, in the presence of water or air moisture.
There are protective methods such as painting or plastic coating, but these methods do have drawbacks. When damaged, sections of the steel will become rusty and the protective coating will fall away, making these types of protection non-lasting and unreliable (always needing continued maintenance).
One of the better methods of protecting steel materials against corrosion is through hot-dip galvanization. With hot-dip galvanization, all the surfaces of the material are dipped into, and completely coated with, molten zinc.
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This is the most popular sheet metal technique for galvanization. The process submerges metal parts in a bath of molten zinc to protect the metal and occurs in three different ways:
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Hot-dip galvanizing limits a steel or iron product’s exposure to the natural elements, protecting it from corrosion and oxidation. Hot-dip galvanizing has been specified to combat steel corrosion for more than 100 years; however, the specification and use of galvanized steel evolves constantly as new markets emerge. Though corrosion resistance is inherent any time hot-dip galvanizing is utilized, there are a number of other benefits including low initial and life-cycle costs, durability, longevity, availability, versatility, sustainability, and aesthetics that lead to the specification of galvanized steel. This sheet metal technique is also economical, can be performed within minutes, and covers hard-to-reach areas of complex product shapes.
This process is when a layer of zinc is bonded to stainless steel using electroplating, which is when a fabricator runs a current of electricity through a saline-and-zinc solution with a zinc anode (an electrode through which conventional current flows into a polarized electrical device).
In electrogalvanizing, the polarized electrical device is a steel conductor.
Compared to hot-dip galvanizing, this sheet metal technique offers lower thickness deposits for comparable to increased performance, a broader conversion coating availability for color options, and brighter deposits.
Metallic spraying is the process of covering a sheet metal product with a metallic coating using a spray of molten particles.
According to Corrosionpedia, “a convergence of business leadership, modern digital technology and industry publication experience”, fabricators first subject the iron or steel “to a high degree of heat to achieve a molten state. The molten metal is then atomized into small particles and sprayed outward onto a surface.
The molten particles [don’t] heat the surface because the heat of a particle is proportional to its size. On contact, the particle flattens out and adheres to the surface as it hardens.”
Flame and arc spraying are sub-methods of this technique, adding anti-corrosion layers and thermal barriers. Other benefits of metallic/thermal spraying include increased durability, wear resistance, modified electrical properties, and additional protection to damaged materials.
Sherardizing is also known as vapor or dry galvanization, sherardizing is named after British metallurgist Sherard Osborn Cowper-Coles.
It involves heating steel products up to 932 degrees Fahrenheit in a closed rotating drum that contains metallic zinc dust and potentially an inert filler, such as sand.
At temperatures above 572 degrees Fahrenheit, the zinc dust evaporates and diffuses into the steel substrate forming a diffusion bond.
This method is ideal for small sheet metal parts and parts that require coating of inner surfaces, as the product must be smaller than the rotating drum.
A huge benefit to this sheet metal technique is that no hydrogen is involved. Therefore, hydrogen embrittlement (when steel becomes brittle due to the introduction and subsequent diffusion of hydrogen into the metal) is excluded.
Aluminum welding presents many more challenges than welding steel or other metals when learning how to weld aluminum. You can find out a guide to aluminum welding or how to weld pipes when they are must-have skills for anyone who takes their welding seriously.
Galvanized sheet metal is one of the most requested products from fabrication shops around the world. In fact, according to the American Galvanizers Association, the world produced more than 4.4 million tons of galvanized steel in .
The most common industries are utility, agriculture, construction, bridge and highway, and recreation. These industries require a variety of sheet metal products, including “structurals, fasteners, tubing, pipe, wire, nails, reinforcing steel, weldments, complex fabrications, guardrail, and posts.”
If so many companies want galvanized sheet metal, what’s the big deal? Here are the benefits of this sheet metal product:
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