Main Difference – Cadmium Plating vs Zinc Plating
In industrial terms, plating refers to the coating of a conductive material with a metal. This coating can be for a decorative purpose, corrosion inhibition, to harden, improve wearability, reduce friction, alter conductivity, etc. There are several plating methods. Cadmium plating and Zinc plating are two such methods. However, cadmium plating is not often used nowadays due to the toxic effects of cadmium metal. Zinc plating is much more commonly used. The main difference between cadmium plating and zinc plating is that Cadmium plating gives a metallic appearance that lasts longer whereas zinc plating does not last for a longer time period.
Key Areas Covered
1. What is Cadmium Plating
– Definition, Advantages of Cadmium Plating, Applications
2. What is Zinc Plating
– Definition, Technology
3. What are the Similarities Between Cadmium Plating and Zinc Plating
– Outline of Common Features
4. What is the Difference Between Cadmium Plating and Zinc Plating
– Comparison of Key Differences
Key Terms: Cadmium, Cadmium Plating, Electrodeposition, Galvanization, Plating, Sacrificial Coating, Zinc, Zinc Plating
What is Cadmium Plating
Cadmium plating is the process of coating a conductive surface with a cadmium layer. Cadmium metal is a soft white metal that can act as a “sacrificial coating” when plated on a surface. Cadmium plating can be used to coat substances such as steel, cast iron, copper, etc. Cadmium corrodes before the covered material. In order to enhance the corrosion protection of cadmium, chromate conversion coatings can be applied over the cadmium layer. This yields a characteristic gold color.
Advantages of Cadmium Plating
- It offers an exceptional bonding surface for adhesives
- It is a preferred coating for salt-environments
- Low electrical resistance
- Outstanding conductivity
- Superior solderability
- Excellent natural lubricity
Figure 1: Cadmium Plating has Aerospace Applications
Applications of Cadmium Plating
- Aerospace applications
- Transportation
- Electronics: for connectors, chassis
- Formed products
- Marine: plating components that are cyclically exposed to salt environment
However, cadmium is a highly toxic substance that can have a cumulative poisoning effect over an extended period of time. Hence it is less or not used nowadays.
What is Zinc Plating
Zinc plating is also known as galvanization and it is the process of coating a conductive substance with a zinc layer. This process is mainly used for iron and steel, as a protection method from rusting. The technique involves electrodeposition of zinc on a substrate.
Figure 2: A Galvanized Surface
Zinc Plating Process
The process of zinc plating is a complicated process. It requires specialized equipment, expertise, etc. Given below are the steps for zinc plating in brief.
- Preparation of the surface – the surface of the substrate (substance on which zinc is going to be applied) is cleaned thoroughly. An alkaline detergent is typically used for this purpose. An acid can be used to remove any rust already present on the surface.
- Preparation of plating solution – an electrolytic solution is used in the plating process. It is referred to as plating bath. It is composed of molten zinc and various other compounds that facilitate the plating process.
- Introduction of electrical current – an electrical current is used to deposit zinc on the substrate surface. The substrate is used as the cathode. A DC current is given to the anode. The current flows from the anode to the cathode through the plating bath, which leads to the deposition of zinc metal on the substrate surface.
- Post-treatment – this involves the washing of the plated surface from water in order to remove contaminants and remaining components. The rinsing may have to be done several times.
Similarities Between Cadmium Plating and Zinc Plating
- Both processes involve coating a substrate with a metal.
- Both cadmium and zinc serve as a sacrificial coating to prevent the substrate from rusting.
Difference Between Cadmium Plating and Zinc Plating
Definition
Cadmium Plating: Cadmium plating is the process of coating a conductive surface with a cadmium layer.
Zinc Plating: Zinc plating, also known as galvanization, is the process of coating a conductive substance with a zinc layer.
Metal Used
Cadmium Plating: Cadmium plating uses cadmium for plating.
Zinc Plating: Zinc plating uses zinc for plating.
Appearance
Cadmium Plating: Cadmium plating gives a metallic appearance that lasts longer than zinc.
Zinc Plating: Zinc plating does not last for a longer time period as cadmium plating.
Use in Marine Environments
Cadmium Plating: Cadmium plating is more suitable be used in the marine environment.
Zinc Plating: Zinc plating is not that much suitable for applications in marine environments.
Temperature
Cadmium Plating: Cadmium plated substrates can be used for high-temperature applications.
Zinc Plating: Zinc plated substrates can be used for low-temperature applications.
Toxicity
Cadmium Plating: Cadmium is highly toxic.
Zinc Plating: Zinc is less toxic compared to cadmium.
Conclusion
Cadmium plating and zinc plating are two electroplating methods used to coat surfaces of conductive substrates in order to prevent these substrates from rusting. The main difference between cadmium plating and zinc plating is that Cadmium plating gives a metallic appearance that lasts longer than zinc plating.
Reference:
1. “Cadmium Electroplating (Nadcap Accredited).” Chem Processing Inc., Available here.
2. “The Zinc Plating Process.” Sharretts Plating Company, 24 Apr. 2017, Available here.
Image Courtesy:
1. “1043938” (CC0) via pxhere
2. “Galvanized surface” By The original uploader was Splarka at English Wikipedia – Transferred from en.wikipedia to Commons (Public Domain) via Commons Wikimedia
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