Zinc plating (also known as electro-galvanising) is a process where zinc is applied by using a current of electricity. While is does provide some rust protection, its thinner coating is not as rust resistant as hot dip galvanising.

 

Are you wondering what the difference between zinc and galvanized is?

Author: Robby

What Does Galvanized Mean?

 

Galvanization is the process of applying a protective zinc coating to steel or iron to prevent rusting.

The most common method is hot-dip galvanizing, where metal parts are fully submerged in a bath of molten zinc.

Zinc plating (also known as electro-galvanising) is a process where zinc is applied by using a current of electricity. While is does provide some rust protection, its thinner coating is not as rust resistant as hot dip galvanising.  However, zinc plating is cheaper and easier to weld.

Be careful when choosing your product! Just because something is labeled 'galvanized' doesn't mean it's hot-dip galvanized. Electro-galvanizing is another term for zinc plating. Use your newly acquired knowledge to ensure you're getting hot-dip galvanized products rather than electro-galvanized ones.

 

Hot dip galvanizing machine for wire

 

What Can Be Galvanized?

 

Hot-dip galvanizing and zinc plating can be applied to a wide range of items, from small nuts and bolts to large structural beams for buildings. In hot-dip galvanizing, the steel is immersed in a large bath of molten zinc, where the coating is applied.

Galvanized items typically have a dull grey, slightly rough surface. In contrast, zinc-plated products are shiny and smooth. While hot-dip galvanized items offer superior rust protection, they may appear less visually appealing due to their rough texture.

 

What Are the Different Galvanization Processes?

Some people may ask: is zinc plated the same as galvanized? Zinc plating is a type of galvanizing, but the two processes differ in the thickness of the zinc coating and the method used to apply it.

The preparation of steel for either hot-dip galvanizing or zinc plating involves similar steps. The steel is first cleaned to remove all oils, paint, grease, mill scale (small flakes of metal), and rust, typically using an acidic bath.

In hot-dip galvanizing, the steel is immersed in a bath of molten zinc at 450°C. The high temperature causes the zinc to bond with the steel, forming a durable, cohesive coating.

Zinc plating, also known as electro-galvanizing, involves immersing the steel in a cold chemical solution containing zinc and applying a layer of zinc using an electrical current. The thickness of the zinc coating is measured in micrometers (μm). Zinc plating typically requires a minimum thickness of 5 μm (0.005 mm) and a maximum of 25 μm (0.025 mm). Coating thickness beyond this range becomes too technical and expensive.

In contrast, hot-dip galvanizing results in a coating with a minimum thickness of 45 μm (0.045 mm) and can exceed 100 μm (0.1 mm), offering more robust protection against rust.

 

Zinc Plating vs Galvanizing: Key Differences

 

1. Application Process

• Zinc Plating: Utilizes an electrochemical process where the metal object acts as the cathode, and zinc is electroplated onto its surface. This method does not provide the same level of bonding strength as hot-dip galvanizing.

• Galvanizing: Involves immersing the metal object into a bath of molten zinc, creating a metallurgical bond between the zinc and the base metal, resulting in a more robust and durable coating.

2. Coverage

• Zinc Plating: May struggle to cover complex shapes and large structures effectively due to its thin layer application.

• Galvanizing: Provides more complete coverage, ensuring that every corner, curve, and crook is protected, especially beneficial for complex shapes and large structures.

3. Environmental Impact

• Zinc Plating: Involves the use of various chemicals, such as cyanide and thiocyanates, which can have environmental implications if not properly managed.

• Galvanizing: Considered more environmentally friendly as it uses pure zinc without additional chemicals or additives.

4. Corrosion Resistance in Harsh Environments

• Zinc Plating: Less effective in highly corrosive environments, where harsh chemicals, saltwater exposure, and acidic conditions can compromise the integrity of the coating.

• Galvanizing: Has an impressive track record of lasting in even the toughest conditions, such as bridges over water or other DOT projects subjected to the elements.

5. Self-Healing Properties

• Zinc Plating: Does not possess self-healing capabilities. Once the thin zinc layer is compromised, the underlying metal is exposed to potential corrosion without any inherent repair mechanism.

• Galvanizing: Has the ability to self-heal. In the event of minor damage or scratches, the zinc layer reacts with moisture and atmospheric conditions, forming protective compounds that prevent further corrosion and effectively repair the damaged areas.

Zinc Vs Galvanized Strength

Galvanized steel is stronger than zinc-plated steel because it has a thicker zinc coating. 

• Galvanizing: The hot-dip galvanizing process coats steel with zinc, making it stronger and more resistant to corrosion. The zinc coating is thicker and more durable than zinc plating, and it can protect steel for decades. Galvanized steel is often used for large structures, like bridges and towers, that are exposed to harsh conditions.
• Zinc Plating: Zinc plating is a method of applying a thin layer of zinc to steel. It's less durable than galvanized steel, and it's more susceptible to corrosion in harsh environments. Zinc plating is often used for small parts, like automotive components and electronic equipment, where surface finish is important.

 

FAQ

How to Distinguish Between Zinc Coated and Galvanized Materials

Thickness: Galvanized coatings are typically thicker, ranging from 2 to 8 mils, while zinc plating results in a thinner layer, usually measuring around 0.2 to 0.5 mils.

Texture: Galvanized surfaces often have a rougher texture compared to the smoother finish of zinc-plated materials.

 

Lifespan and Maintenance

Zinc Plating: The lifespan varies depending on the thickness of the coating, the type of environment, and the presence of corrosive elements. Generally, it provides moderate corrosion protection and can last from a few months to several years.

Galvanizing: Lasts significantly longer than zinc plating, offers more complete coverage, and requires less maintenance.

 

Zinc plated vs galvanized, which is Better?

Both processes have their merits and are suitable for different applications:

Zinc Plating: Ideal for aesthetic or tolerance reasons, providing a relatively low-cost, protective, and attractive coating for a variety of products.

Galvanizing: Preferred for heavy protection, especially in harsh environments where long-lasting corrosion resistance is critical.

 

How Long Does Zinc Plating Last?

Material is immersed in molten zinc at a temperature of around 450 degrees until the temperature of the work is the same as the Zinc. During this process, the molten zinc reacts with the surface of the steel to form a series of zinc/iron alloys. These alloy layers protect steel from corrosion for 30-40 years and more.

 

At Ruisite, we understand the importance of choosing the right finishing process for your specific needs. Our expertise in both zinc plating and galvanizing ensures that your products receive the highest quality protection and performance. Contact us today to discuss your project requirements.