Choosing the metal for your products is one of the most important decisions for your project. The choice of metal can affect the durability, cost, and overall success of the project. Galvanized metal is one of the most popular and versatile metal surfaces due to its greater strength, durability and formability.
In this article we provide a comprehensive overview of metal galvanizing processes. Next, we will discuss the various advantages and applications of galvanized metal sheets.
Electroplating Definition
Galvanizing is the process of coating the surface of a metal, alloy or other material with zinc. It is a surface treatment technique that serves aesthetic and rust prevention purposes. Because zinc acts as a sacrificial coating, it protects the underlying substrate.
Therefore, galvanizing is generally used to extend the service life of metal parts. The versatility of this metal coating makes it suitable for a wide range of applications across diverse industries, including automotive, solar, electronics and construction.
What is galvanized metal?
Galvanized metal is simply metal that has gone through the galvanizing process. This process involves applying thin layers of zinc to the surface of the metal to protect it from corrosive elements. This usually involves dipping clean, oxide-free metal into molten zinc to create a layer of zinc on the metal.
The coating then metallurgically bonds to the metal surface and acts as a sacrificial anode. As a result, the coating gives the metal durability and longevity.
What types of metal can be galvanized?
The most common metals suitable for galvanizing are steel and iron. However, other types of metal can also be galvanized. Generally, all ferrous metals such as cast steel, cast iron, malleable iron, hot-rolled steel and cold-rolled steel can be galvanized.
However, galvanic coatings do not form on many other materials. Because iron is important in the electroplating reaction, galvanic coatings do not form on metals such as copper or aluminum. A coating may form on materials such as chrome-molybdenum steel, but many stains remain.
Galvanizing process: How does galvanizing protect the base metal?
Electroplating is the process of adding a layer of zinc to the surface of metals such as steel and iron. There are different galvanizing processes. Therefore, the process varies depending on the technique chosen. However, they are all based on the basic principle of surrounding steel or iron with zinc, which can be in liquid or powder form.
When zinc is added, the iron present in the metal substrate reacts with the zinc and tightly bonded alloy coatings are created. It is a relatively simple coating that produces a fairly thick coating. The entire process can be divided into three phases:
- Metal surface preparation
- The actual galvanization
- Surface treatment after galvanizing
In general, galvanizing protects metal according to the following principles:
- The zinc coating protects the base metal from corrosive substances such as acids, alkalis and bases, gases, etc.
- Zinc acts as a sacrificial metal. When the coating is scratched, the zinc releases its anode instead of the base metal, protecting it from rust.
- Zinc's ability to corrode more quickly than the base metal is an excellent way to protect the metal. Some manufacturers add chromium to galvanized metal as a “special agent” to make the zinc rust even faster.
However, preparation and post-treatment methods determine the effectiveness of the galvanizing process. Improper preparation affects the reaction between the base metal and molten steel. Inadequate post-treatment can also affect the final appearance of the galvanized coating. This, in turn, affects the overall quality of the product.
Different galvanizing methods
There are different galvanizing processes, each process having its own characteristics and advantages. Here's an overview:
Hot dip galvanizing
As the name suggests, this process is accomplished by dipping the base metal into a bath of molten zinc. Before actual galvanizing, machinists must clean the base metal chemically, mechanically, or both. Cleaning is a preparatory process to ensure a high-quality bond between the metal and the zinc coating. After cleaning, the metal is treated with flux to remove any oxide residue.
This is followed by the process of immersion in a heated zinc pool, often maintained at a temperature of around 460°C (860°F). A metallurgical bond then begins between the zinc and the metal substrate. After the metal is removed from the bath, it reacts with oxygen to form zinc oxide. This zinc oxide also reacts with carbon dioxide to form zinc carbonate, which is the final protective layer.
Hot dip galvanizing is a quick and economical method and can be used on both simple and complex sheet metal structures. However, it may happen that the metal coating is uneven.
Pre-galvanizing
The pre-galvanizing process is similar to hot-dip galvanizing. However, it is carried out in the first phase of production (in the melt shop). This process involves rolling metal sheets through a mechanical or chemical cleaning agent to prepare the metal for galvanizing. After cleaning, the machinist passes the base metal through a pool of molten zinc before immediately rewinding it.
This process ensures rapid galvanization of large rolls of steel sheet and guarantees a more uniform coating. However, there may be some uncoated and exposed areas during the production of pre-galvanized metal. For example, edges remain free when longer sheet metal rolls are cut into smaller pieces.
Galvanization
In contrast to the two processes described above, electroplating does not use a molten zinc bath. Instead, an electrical current is introduced into an electrolyte solution before it is applied to the steel material. The electric current transfers the zinc ions to the metal substrate.
In this method of metal plating, positively charged zinc ions are electrically reduced to metallic zinc. The zinc metal is then deposited on a positively charged metal (steel or iron). Manufacturers also add grain refiners to ensure a smooth zinc coating on the metal. Like pre-galvanizing, galvanizing is also used in the early stages of the product development process on long rolls of sheet metal.
This process applies a precise and uniform layer thickness to the metal. However, coatings with this process are generally thinner than with hot-dip galvanizing.
Galvanizing and tilting
Galvannealing is a combination of hot-dip galvanizing and annealing. The objective of this process is to produce galvanized steel with a special coating. The annealing and hot-dip galvanizing processes occur instantly and produce a matte gray surface.
The hot-dip galvanizing process generally occurs before the coated metal passes through the air knives. Air knives help remove excess zinc from the metal. The metal is then briefly heated to 500 to 565 °C in an annealing furnace. The zinc and iron layers then diffuse into each other to form zinc-iron alloy layers.
The galvanized steel thus produced is resistant to welding and the surfaces guarantee excellent paint adhesion.
Advantages of galvanizing sheet metal
In general, galvanization gives the metal substrate corrosion-resistant properties. This, in turn, offers several advantages to sheet metal. Here are some of the benefits of metal galvanizing:
1. Improve durability
Galvanizing produces one of the most durable coatings in the industry today. Industrial galvanized steel can last more than 50 years in a normal environment. If exposed to heavy water, it can last more than 20 years. In fact, if you use an average coating that is 85 microns thick, you can expect your steel structure to last up to 100 years.
The process creates a coating thickness that helps the metal meet current corrosion protection requirements. In most cases, no maintenance is required, which increases product reliability.
2. Provides triple protection for base metals
Galvanizing protects your metal in three ways:
- Forms a physical barrier. This barrier is metallurgically bonded to the metal and protects it from the elements. The highly durable coating provides seven times stronger adhesion than organic paints. Therefore, you can be sure that your metal will last longer without any maintenance.
- Provides protection to victims. Zinc sacrifices its anode when small scratches occur on the galvanized metal. Zinc corrodes preferentially rather than the underlying metal, providing long-term protection.
- Prevents lateral sliding. Lateral creep is a form of corrosion that occurs when rust deposits build up on exposed steel. Let's say there is an unusual case where the galvanized coating is damaged and the bare steel is exposed. In this case, the zinc coating limits the damage to prevent this type of damage.
3. Get full coverage
Galvanizing not only provides superior strength and durability, but also excellent coverage. This ensures that even the most sensitive areas of the metal remain protected for a long period of time. The initial cleaning process prepares and prepares the metal surface for coating. This means that the zinc layer adheres better to the metal.
Furthermore, hot-dip galvanizing also allows the coating of the internal surfaces of hollow bodies. This protects the structure from the inside out. In contrast to spray and brush coatings, hot-dip galvanizing also forms layers on important edges and corners.
Therefore, both small and large components can be equally protected against corrosion.
4. Reliable coating
Iron elements in steel and iron alloys are prone to rust. However, the combination of zinc and iron elements helps to form a protective layer between the metal and moisture or oxygen. The metallurgical bond formed provides secure and complete protection from the start. Even depressions and sharp corners can be protected with this coating and thus resistant to damage.
5. Value for money
Unlike many other metal treatment processes, galvanized metal is ready for immediate use. The high-performance coating created by this process makes other part finishing processes unnecessary. Plus, in most cases you don't need to worry about maintenance. All of this combined reduces the overall cost of galvanized metal.
6. Fast processing
After preparing the metal and the molten zinc is ready, galvanizing takes just a few minutes. Although metal preparation must be thorough, it does not need to be very time-consuming. As long as you work with the right company, the process will be seamless and time-efficient. Completing your deliverables in a short period of time will help you achieve your business goals faster.
Galvanized Metal Industrial Applications
Galvanized metal has a wide range of applications, from automobile bodies to drinking water pipes, nuts and bolts, electrical wires, etc. Its wide use is due to its cost-effectiveness and ability to create durable coatings. It is one of the best options if your component is exposed to harsh environmental conditions.
Below are some industries where galvanized sheet metal is valuable:
Wind and solar industry
Once installed, solar systems require continuous operation and any repairs or maintenance cost money. Due to its ability to prevent corrosion, galvanized steel is often used in solar systems. Because it emits no emissions and requires decades of maintenance, it is also known as “environmentally friendly”. Even when exposed to the harsh climate of solar systems, hot-dip galvanized steel provides corrosion protection that typically lasts decades.
Auto Industry
Galvanized bodies are now standard in automobile construction, although in the past manufacturers limited this to luxury vehicles. About 80% of a car's body is made up of the body, which is entirely made of galvanized steel. The rust resistance of galvanized steel makes it a useful tool for automotive prototyping because it allows companies to offer “anti-rust guarantees” to consumers.
Telecommunications industry
Due to their height and frequent difficulty in access, telephone lines are a major maintenance challenge. To be successful, they need the strongest and most reliable materials. Telephone cables and equipment boxes can be made from galvanized metal. This reduces the risk of damage and requires no maintenance.
construction industry
Galvanized steel has been a staple in the construction industry for over a century, whether for commercial or residential use. In addition to its durability, it is also used in construction due to its aesthetic appeal. Galvanized steel has a contemporary look thanks to its “shine” and is widely used by designers in modern architectural project concepts.
Additionally, it is also used for a variety of smaller structural components, including fences, railings, gutters, pipes, posts, and more.
Concluding
Galvanized metal offers several benefits, including durability, corrosion resistance and cost-effectiveness. This type of metal is useful for a variety of applications in many industries. If your applications require products exposed to extreme environmental conditions, you should choose galvanized sheets.
Common questions
How do I know if a metal is galvanized?
The pattern on the metal surface will indicate whether it is galvanized. Galvanized metal often has a distinctive crystal-like pattern called a “spangle” pattern. Because this process also adheres a layer of zinc to the metal, you can also verify this using thickness measurement, laboratory testing, and electron spin resonance (EPR).
Which is better, aluminum or galvanized steel?
In industrial processes where components are exposed to corrosive materials, galvanized steel is preferred over aluminum because it offers better corrosion resistance than aluminum. However, aluminum products are preferred when applications require lightweight materials and efficient heat conduction.
Can you engrave galvanized metal?
Yes, it is possible to engrave galvanized steel. To do this, you need to remove as much of the zinc layer as possible with fine sandpaper or a slightly abrasive sponge. The acid etching then hits the steel and etches the desired design into the metal.
