Why Galvanize Materials?

Every metal structure must be durable and maintain this property for as long as possible. There is no doubt that steel is incredibly strong, but many of its alloys are prone to damage under certain environmental conditions. In terms of protecting metal from corrosion, galvanization seems to be the best choice. Let's first take a look at some of the advantages of galvanization and why it's necessary.

What is Galvanized Steel?

The galvanizing process involves applying a thin layer of another metal coating to an existing metal. In most cases, zinc is used as the coating material for metal structures. This zinc protective layer shields the metal from the surrounding environment. Galvanized steel is able to withstand harsh conditions, making it long-lasting and ideal for outdoor use.

Advantages of Galvanized Steel

1. Enhanced Protection
The primary purpose of galvanization is to prevent rust; this is why galvanized steel surfaces are covered with zinc oxide. The idea behind galvanization is that the zinc layer must corrode first, allowing the steel to remain safe for a longer time. Without the zinc coating, the metal would be more susceptible to corrosion, and the corrosion would accelerate due to the metal being exposed to the natural environment.

2. Longer Lifespan
This is a result of the coating's protective performance. Research shows that, under normal conditions, a piece of industrial galvanized steel can last up to 50 years. In highly corrosive environments with significant water contact, the same metal piece can last up to 20 years.

3. Better Appearance
This advantage is somewhat subjective, but most people agree that galvanized steel looks better compared to most steel alloys. Typically, it is brighter and may even have a shinier appearance under certain types of coatings.

Applications of Galvanized Steel

Zinc-coated steel has a wide range of uses. In fact, it is employed in many industries such as construction, energy plants, agriculture, and sports sectors. Galvanized steel plays a crucial role in building roads, buildings, bridges, railway tracks, gates, signal gantries, storage containers, and sculptures. Therefore, whenever corrosion must be avoided, galvanization is necessary to secure the metal.

Methods of Galvanizing Steel

There are several methods for galvanizing:

1. Hot-Dip Galvanization
In the process of galvanizing steel, the steel is dipped into a bath of molten zinc. Hot-dip galvanization (HDG) involves three basic steps: surface preparation, galvanizing, and inspection.

• Surface Preparation
  In this stage, prefabricated steel is prepared for galvanizing by going through three cleaning stages: degreasing, pickling, and fluxing. Without this cleaning process, galvanization would be impossible, as zinc will not react with impure steel.

• Galvanizing
  After surface treatment, the steel is immersed in 98% molten zinc at 830°F. The angle at which the steel is dipped ensures that air escapes from tubular shapes or other pockets, allowing zinc to flow through and cover the entire steel structure. The iron in the steel reacts with the zinc, forming a zinc-iron alloy coating, with pure zinc deposited on the exterior.

• Inspection
  The final step is to inspect the coating. A visual check is conducted to ensure that no uncoated areas are left, as zinc will not adhere to unclean steel. Magnetic thickness gauges are also used to determine the thickness of the coating.

2. Electro-Galvanization
Electro-galvanized steel is made through an electrochemical process. In this process, steel is immersed in a zinc bath, and an electric current is passed through it. This process is also known as electroplating.

Before electro-galvanizing, the steel must be cleaned. Here, zinc acts as the anode, protecting the steel. Zinc sulfate or zinc cyanide is used as an electrolyte for electrolysis, where the steel, serving as the cathode, is protected from corrosion. The electrolyte causes zinc to adhere to the steel surface. The longer the steel remains in the zinc bath, the thicker the coating.

3. Sherardizing
Galvanizing involves forming a similar zinc coating on the surface of iron or steel to prevent corrosion.

In this process, steel is placed in a container with zinc, and the container is sealed and heated to a temperature below the melting point of zinc. The result of this reaction is the formation of a zinc-iron alloy with a solid outer layer of pure zinc that adheres to the steel surface, providing significant corrosion resistance.

4. Metal Spraying
In metal spray galvanization, charged or atomized molten zinc particles are sprayed onto the steel surface. This process is carried out using a gun-like spray device or a specialized flame.

Before spraying the zinc coating, all contaminants such as unwanted surface coatings, oil, and rust must be removed. After cleaning, the atomized molten zinc particles are sprayed onto the roughened surface, where they solidify.

How Long Does the Zinc Coating Last?

As for durability, it generally depends on the thickness of the galvanized layer or other factors such as the type of environment, the type of galvanization used, and the quality of paint or spray. The thicker the galvanized layer, the longer the lifespan.

Compared to cold galvanizing, hot-dip galvanizing tends to be more durable because the coating is thicker and more resilient. Hot-dip galvanization involves dipping the metal in molten zinc, while in cold galvanization, one or two layers are sprayed or brushed on.

In terms of durability, hot-dip galvanized coatings can last over 50 years under any environmental conditions, while cold galvanized coatings typically last a few months to a few years, depending on the thickness. Therefore, selecting high-quality zinc coatings and protecting them over time is crucial for maximizing resistance to corrosion, wear, and rust.