What is Galvanized Steel?
Galvanizing, or galvanization, is a manufacturing process where a coating of zinc is applied to steel or iron to offer protection and prevent rusting. There are several galvanizing processes available, but the most commonly offered and used method is called hot-dip galvanizing.
Galvanized steel is among the most popular steel types because of its extended durability, having the strength and formability of steel plus corrosion protection of the zinc-iron coating. The zinc protects the base metal by acting as a barrier to corrosive elements, and the sacrificial nature of the coating results in a long-lasting and high-quality steel product.
This versatility makes it applicable to a variety of projects and industries, including agriculture, solar, automotive, construction, and so on. Below, we aim to provide a comprehensive description of how galvanized steel is processed, different galvanization methods, its benefits, and how it is used in these various industries.
The steps in the galvanizing process are as follows:
- The steel is cleaned in a degreasing solution
- After being cleaned, the steel is pickled by being lowered into a vat of diluted hot sulfuric acid
- The steel is then fluxed in an aqueous solution (typically zinc-ammonium chloride)
- After the flux, the steel is galvanized through immersion in a vat of molten zinc
- Afterward, the steel is inspected for consistency and a complete coating
How to Galvanized Steel?
There are a few methods of galvanizing metal. The most common method is the hot-dip galvanization process. This method of galvanization creates a nice, thick layer of zinc on top of the base metal, which makes it extra resistant to corrosion. For the most part, the hot-dipping process doesn’t sacrifice the structural integrity of the metal, but some very high-strength steels can suffer from hydrogen embrittlement.
The steel used in car bodies is also galvanized, but because layers of decorative paint need to be applied afterward, they use a different galvanization process. This is because the zinc layer from the hot-dip method is too thick, and causes issues with the paint adhesion.
Instead, automobiles use the electro galvanization process. A solution of salt water (saline) and zinc is put into a tank, and the steel or base metal is dipped inside. An electrical current is run through the vat, and the zinc bonds to the base metal!
A special form of galvanizing, called Sherardizing, is used to create a zinc coating on iron or copper products. It was created by metallurgist Sherard Osborn Cooper-Coles and patented around 1900.
The metallic parts that are to be galvanized are put inside of a closed, rotating drum along with zinc powder, and sometimes filler-like sand. The drum is then superheated to 500C. At temperatures above 300C, zinc turns into a vapor and this vapor penetrates the metal turning inside of the drum.
This process is also called “dry galvanizing” because there are no liquids used.
This is probably how many small parts around your home, like screws or nuts and bolts, have been galvanized. This process doesn’t use any hydrogen, so hydrogen embrittlement can’t happen during this method of galvanizing.
What are the Advantages of Galvanized Steel?
Many different industries utilize galvanized steel primarily because it has such a wide array of benefits for industries to take advantage of, including having:
- Low initial cost compared to most treated steels. In addition, galvanized steel is immediately ready to use when delivered. It does not require additional preparation of the surface, inspections, painting/coatings, etc. sparing companies more costs on their end.
- Longer life. With galvanization, a piece of industrial steel is expected to last more than 50 years in average environments, and can last over 20 years with severe water exposure. There is no maintenance required. The increased durability of the steel’s finished product also increases the product’s reliability.
- The sacrificial anode ensures that any damaged steel is protected by the surrounding zinc coating. It doesn’t matter if the steel section is completely exposed; the zinc will still corrode first. The coating will corrode preferentially to the steel, creating a sacrificial protection to the areas that are damaged.
- Rust resistance from the zinc coating. The iron elements in steel are incredibly prone to rusting, but the addition of zinc acts as a protective buffer between the steel and any moisture or oxygen. Galvanized steel is very protective, including sharp corners and recesses that couldn’t be protected with other coatings, making it resistant to damage.
Where is Galvanized steel used?
Galvanized metals are used everywhere! The bodies of cars and many bicycles are made from galvanized metals. Some drinking water pipes are still made from galvanized steel. Cool rolled sheet metal is also frequently galvanized. Nuts, bolts, tools, and wires of all kinds are now galvanized because it is a cheap process, and helps boost the metal’s lifespan!
Galvanized steel, in particular, is often what is used in modern “steel frame” buildings. Galvanized steel is also used to create structures like balconies, verandahs, staircases, ladders, walkways, and more. Galvanized metal is the ideal choice if your project will live outside after it’s done. Fences, roofs, outdoor walkways, these are all great choices for galvanized metal!
Wind & solar industries
Solar projects must have a continuous workflow once installed and any repairs/maintenance results in disruption to service (a.k.a. revenue loss). This means that hot-dipped galvanized steels are popular in solar projects for their corrosion protection.
It is also popular for its ‘environmental’ friendliness because it does not produce emissions and ensures decades without maintenance. For example, it is often utilized in the agriculture industry because the equipment is susceptible to being easily corroded, creating a demand for tougher, more resilient equipment.
Hot-dip galvanized steel provides corrosion protection that can often last for decades, even when exposed to the harsh environment of farming.
Though only used on luxury models up until the 1980s, the use of zinc-coated bodies for automobiles is now the norm in auto manufacturing. The ‘body-in-white’ of a car makes up about 80% of the body, all using galvanized steel.
The rust resistance of galvanized steel is also a good marketing tool for the automotive industry because it can provide ‘anti-rust warranties’ to customers.
Whether for residential or commercial, the durability of galvanized steel has made it popular for over a century in the construction industry. It is also selected for construction because of its aesthetics; The ‘shine’ that galvanized steel provides gives it a contemporary feel and is popular in modern architectural designs.
Also, it isn’t just used for large structural pieces but things like fencing, gutters, rails, tubing, poles, and much more.
Phone lines are not an easy maintenance job; they are tall and often difficult to reach. Hot-galvanized steel can be used on phone wiring and equipment boxes which decreases the risk of damage and the need for maintenance at all.
What Types of Metal Can Be Galvanized?
Iron and steel are the two most common types of metals that are galvanized. However, they are not the only types of metal that can receive this treatment.
Most ferrous metals are able to be galvanized, while most non-ferrous metals are not able to be galvanized. If you are unsure if a metal is ferrous or non-ferrous, a magnet can help enlighten you. If a magnet sticks, you have a ferrous metal. If the magnet doesn’t stick, you are dealing with a non-ferrous metal.
What Are the Advantages of Galvanized Metal?
Galvanization is primarily performed to prevent your main metal material from rusting or corroding. When a layer of zinc is added to a sheet of metal, the zinc itself will rust or corrode. While this may sound like a negative, it is actually a positive.
Since the zinc is rusting or corroding, it is preventing or slows the more expensive and vital metal from rusting or corroding. This helps to protect your more important metal source from the damaging effects associated with rust and corrosion.
Helping to slow or protect against rust and corrosion can help extend the lifespan of your metal and reduce the amount of maintenance the metal may need.
The other major benefit associated with galvanized metal is that the zinc coating is long-lasting. You can purchase many products and sealers to protect your metal against rust and corrosion. Many of these coatings wear off in a matter of years due to weather exposure. Zinc can last upwards of 50 years, which prevents you from having to coat your metal again in the future.
Are There Any Drawbacks to Galvanized Metal?
One of the biggest drawbacks to galvanized metal is that the galvanization process helps to hide imperfections, flaws, and problems with the metal. As such, you may miss problems with metal that require immediate repair or maintenance.
Another drawback to galvanized metal is that the coating is not always smooth. When it is used inside of pipes, it can lead to items getting stuck on the rough surface, which leads to blockages and obstructions within the pipe.
Galvanized Steel vs Stainless Steel: Which Is the Better Choice?
Galvanized steel is almost the same price as untreated structural steel. Stainless steel costs four to five times as much as galvanized steel and untreated structural steel. Niobium alloys are even more expensive.
Galvanized steel is coated with a thin layer of zinc that helps guard against corrosion. It’s commonly used in nails, screws, bolts, nuts, and other kinds of fasteners. Galvanized steel usually stands up well to water exposure as long as it’s not saltwater.
Stainless steel, on the other hand, is made by adding chromium to molten steel. Because of its strength and resistance to rust, stainless is the primary metal used in construction. Stainless doesn’t mind water, even if it’s salty, so it’s great for marine environments.
You should stay away from stainless, though, if there’s any chance two pieces might come into contact with one another. Friction can rub through the coatings and cause the two parts to weld together. And don’t use stainless steel around pools or other places where it might be exposed to chlorine. Chlorine degrades the coating on the metal and causes rust.
Which Kind of Steel Stands up Better?
As you look through the characteristics of these two types of steel, you can see they are very different from each other. Both kinds of steel are applicable to a huge range of products, but one type will always be a better choice than the other.
There are situations in which you need to stay away from stainless steel. This product stands up to salt water, but it is quickly degraded after exposure to chlorinated water. You also need to avoid any design in which two stainless steel components generate friction against each other. They can weld themselves together.
As great as galvanized steel is, there are also situations in which the choice of galvanized steel needs additional consideration. Usually, steel should be welded before it is galvanized, not after. Welding steel after it has been galvanized burns away the protective layer of zinc at the weld. It may be necessary to galvanize galvanized steel after it is welded to protect the joint.
If you are building the rocket that will send the Space Force to Mars, you will probably need to work with stainless steel. You will also need stainless steel if you get a contract to build an ocean-bound submarine. But for most down-to-earth uses of steel on land, your most economical choice, in terms of both material and labor costs and the life of the project, will be galvanized steel.