Zinc plating process

The Zinc plating process- everything you need to know

Metals such as iron and steel are prone to corrosion. If you are looking for ways to protect your metallic products from rusting, you’re not alone. Countless industries are now turning to zinc plating for help.

If you’re hearing about this for the first time or want to learn more about the zinc plating process and its benefits, you’ve come to the right spot. I’ll be discussing all this and more. So hop on board, let’s get down to business.

What is Zinc Plating?

Zinc plating (also known as zinc electroplating) is exactly what it sounds like. It’s the process of covering a metal object (substrate) with a layer of zinc with the help of electricity. This extra layer remains intact for a long time, protecting the substrate from rust and corrosion.

Electroplating zinc onto metal is a complex process that requires special equipment and considerable technical knowledge. While you can DIY zinc plating projects at home, the electrodeposition of zinc on metal components is something factories do on a large scale. For this reason, I’ll describe the steps of the industrial zinc plating process in more detail.

A Closer Look at the Zinc Plating Process

There are different ways to apply zinc coatings, including zinc electroplating, hot dip galvanizing, zinc metal spraying, thermal diffusion galvanizing, etc. Today, I’ll discuss one of the most popular types of zinc coating – electroplating. Here’s an outline of the process in industries:

Step #1: Surface Cleaning

Before beginning the process, it’s crucial to clean the metallic object. If any rust, debris, dirt, or oil is present on the surface, the zinc coating will not bond to the surface. Inefficient cleaning hinders the quality of the zinc coat and causes it to peel or blister over time.

Cleaning the substrate for electroplating entails soaking the component in an alkaline bath for 5 to 10 minutes at about 150° F. This helps remove contaminants such as soil and dirt from the surface. The object is then rinsed to prevent contamination of further processes.

Some vendors additionally clean the metal object at a micro-level by passing an electric charge through it.

Step #2: Pickling

Right after the alkaline bath, the substrate is pickled, i.e., it’s subjected to an acid treatment (usually sulfuric acid or hydrochloric acid). This helps remove oxides, such as rust and mill scales, from the surface that often form during manufacturing or storage. The object is again washed with water after pickling and allowed to dry.

The amount of time a substrate is dipped in the acid, the kind of acid used, and the temperature of the treatment all depend on the metal that needs to be coated or the thickness of the scales present on it.

Step #3: Preparing the Plating Bath

The metal object is immersed in a plating bath consisting of a zinc ionic solution. This solution is specially formulated to facilitate the zinc plating process. Sometimes vendors may add other chemicals to enhance the properties of the original product.

Vendors also use different zinc electrolyte solutions, such as acid or alkaline zinc. The solution that is used determines the thickness of the zinc coating and, ultimately, the product’s durability. For example, an acid zinc solution delivers a faster electrodeposition rate with better coverage. On the other hand, alkaline zinc may be slower, but it offers better coating thickness.

Step #4: Coating the Component with Zinc

The plating process involves passing an electrical current through the plating bath (hence the name electroplating). The component to be coated acts as a cathode, while zinc is the anode. Both are immersed in the aqueous solution, and DC is introduced to the bath. The zinc in the anode dissolves into the plating bath and migrates to the cathode. The zinc ions are deposited onto the surface of the substrate, creating a layer of zinc on it.

Vendors use several methods to apply zinc coatings, such as rack plating and barrel plating. Rack coating is ideal for delicate or large parts, while barrel plating is a better option for smaller or more durable parts.

Step #5: Post-Electroplating Treatment

Once the metal object is coated with zinc, it is rinsed with water and left to dry. The substrate can be treated with passivates or sealers if additional protection is required.

How Does Zinc Plating Protect a Metallic Object?

Since the entire object is coated in a protective layer of zinc, the actual metal (iron or steel) does not come in contact with the atmosphere. Instead, the zinc layer reacts with atmospheric oxygen to create zinc oxide. This compound then reacts with the water vapor in the atmosphere to produce zinc hydroxide.

But the action does not stop here. The zinc hydroxide further reacts with the carbon dioxide in the air to produce a thin, gray layer of zinc carbonate. Surprisingly, zinc carbonate adheres very strongly to the surface of the underlying zinc. More importantly, it’s impermeable, insoluble, durable, and unremovable. So as you can see, this protective layer prevents the metal object from corrosion by preventing it from interacting with the atmosphere.

Benefits of Zinc Coating

Many industries utilize zinc coating steel parts. Here is why:

  • The zinc coating offers resistance to rusting and corrosion.
  • Electroplating creates a lightweight, protective layer.
  • The zinc electroplating process is a cost-effective method of protecting metal objects.
  • Enhances the aesthetics of metal objects by helping to alter the finish or color
  • The zinc electroplate helps increase the strength of the original product.
  • Zinc tolerates temperatures as high as 120° F.
  • Vendors provide the flexibility of customizing the zinc plating process depending on the client’s needs.
  • Zinc electroplating is a relatively eco-friendly process. Moreover, zinc is recyclable.

Over to You

The zinc plating process comes with a boatload of benefits. However, the secret to achieving a good quality zinc coating lies in using the right vendors.

At Midwest Distribution LLC, we provide top-notch, affordable zinc coating services. Our employees have years of experience in the process that guarantees to protect your merchandise from corrosion. We already offer zinc-coated services to a range of industries. So, consider coating your products with a durable, protective zinc layer.


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Jon R Marler

Marler is US Air Force Veteran with a career spanning 38 years owning and operating a commercial, multi-state real estate development company, material handling distribution network, and a management consulting firm.

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