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Comparing Zinc Plated and Galvanized Steel

Zinc plated and galvanized steel are two protective coatings that are designed to enhance the corrosion resistance of steel structures. Zinc plating offers moderate protection for indoor environments, while galvanizing provides robust defense against rust, particularly in harsh environments. 

In this article, we’ll talk in detail about the processes of zinc plating and galvanized steel, the main differences between the two, and their applications. 

What is Zinc Plating?

Zinc plating or electroplating is a surface treatment process used to coat a metal object with a layer of zinc. It protects against corrosion and improves appearance. Zinc coated steel is used in various industries. For example, it’s used in the automotive industry, construction, electronics, marine industry, medical equipment, etc. 

The zinc plating process starts with cleaning the metal object to remove contaminants. The next step is to perform a pre-treatment process that activates the surface and promotes adhesion. Next, the object is immersed in a solution containing zinc ions. 

A direct current is then applied between the metal object and a zinc electrode. In this way, zinc ions migrate and adhere to the surface of the metal object. The zinc ions are reduced and deposited onto the surface, forming a layer of zinc coating. After plating, the coated object is usually rinsed and passivated to enhance corrosion resistance and improve the appearance of the coating. 

Zinc plating is corrosion-resistant. It protects against rust or other types of corrosion. It's also quite flexible and is used for a variety of metal objects. Zinc coating is known to be cost-effective and durable. The zinc coating thickness can be adjusted, by changing the parameters during the plating process. 

The last question remains: is zinc plating rust proof? Over time, the zinc coating may corrode, especially in harsh environments or if the layer gets damaged. However, the corrosion occurs more slowly compared to untreated metals.

What is Galvanized Steel?

Galvanized steel is coated with a zinc layer to make it corrosion-resistant and durable. It protects the steel from rusting and corroding even in challenging environments.

Galvanizing steel means immersing a steel object in a bath of molten zinc or applying a zinc-rich coating. There are two main methods of galvanizing: hot-dip galvanizing and continuous galvanizing. Hot-dip galvanizing means immersing the steel object entirely in a bath of molten zinc, while continuous galvanizing applies a zinc coating to the steel surface through a continuous process. 

Hot-dip galvanizing is the most common method of galvanizing steel. First, the steel object is cleaned to remove any surface contaminants. Next, it is dipped into a molten zinc bath at around 450°C (850°F). The zinc bonds with the steel surface to form a metallurgical bond. In this case, zinc coating is thicker and more robust. Hot-dip galvanizing is great for big building parts, as well as ironwork, metal furniture, and architectural components.

Continuous galvanizing means passing a steel strip or sheet through zinc-coating baths. The process includes cleaning, annealing, applying a zinc coating, and cooling. Continuous galvanizing is more suited for flat sheets and smaller components produced in high volumes.

Same as zinc plating, galvanized steel is durable and cost-effective. It is also more flexible from an aesthetic perspective since it can be painted over or coated. Galvanized steel is corrosion-resistant and requires minimal maintenance. 

Zinc Plated vs Galvanized Steel: Evaluating the Differences

  • Zinc plating has a thinner coating and is more flexible. It is often used for smaller and intricately shaped components. It's good for things that need to stay their original size, like medical tools, glasses lenses, and dental implants. 
  • Galvanized steel has a thicker coating and is less flexible. It is better suited for larger structural components and for items where a bit of extra thickness won't cause issues.
  • While zinc plating has good corrosion resistance, it is less effective than galvanizing in harsh or outdoor environments. It has a moderate level of protection against rust. 
  • Galvanizing offers better corrosion resistance due to its thicker zinc coating. 
  • Zinc plating is more cost-effective than galvanizing. It requires less zinc and processing time. Galvanizing involves a thicker zinc coating and a more complex process. However, the enhanced corrosion resistance and durability justify the higher initial investment.
  • Zinc plated steel is moderately durable. It is suitable for indoor or controlled environments and can provide reasonable protection against corrosion for a certain period. 
  • Galvanized steel is known for its superior durability. When choosing between zinc or galvanized for outdoor, galvanized steel with its thick coating and metallurgical bond is more suitable. It’s also used for marine and industrial applications. 
  • Zinc plating allows for better control over coating thickness. Galvanizing involves a more standardized coating thickness, typically thicker than zinc plating. While some control over thickness is possible, it is less customizable compared to zinc plating. 

    Applications of Galvanized vs Zinc Plated Steel

    Cable Trays and Conduits

    Zinc plated steel is commonly used for cable trays and conduits in indoor or controlled environments. It offers moderate corrosion resistance and is suitable when the trays and conduits are not exposed to harsh weather conditions.

    Galvanized steel is a better choice for cable trays and conduits that will be installed outdoors or in environments with exposure to moisture, chemicals, or corrosive agents. It has a thicker coating, so the protection against corrosion is better.

    Grounding and Bonding

    Zinc plated steel can be used for grounding and bonding components in non-corrosive indoor environments.

    Galvanized steel is used for grounding and bonding components that will be installed outdoors or in areas with high corrosion potential because of high corrosion resistance.

    Fasteners and Fittings

    Zinc plated fasteners and fittings are suitable for applications with moderate corrosion requirements. These include indoor furniture, light fixtures, and some mechanical assemblies. Holder kits are also available.

    Galvanized fasteners and fittings are used for outdoor structures, construction, industrial equipment, etc. They are used for applications where corrosion resistance is critical. With galvanized coating’s durability, it helps to ensure the functionality for a long time.  

    Cable Armor

    Zinc plated cable armor may be appropriate for indoor installations where the cable will not be exposed to harsh conditions. 

    Galvanized cable armor is more suitable for outdoor or industrial applications where the cable armor will be subjected to moisture, temperature variations, and potential physical stress. The enhanced corrosion resistance of galvanized steel ensures the armor's reliability.

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    Comparing Zinc Plated and Galvanized Steel