Principles of Electroplating

Electroplated materials have many applications in our lives.
••• Medioimages/Photodisc/Photodisc/Getty Images

Electroplating is the surface treatment and finishing of metals or nonmetals. An electrochemical reaction is used to form a metallic coating from an aqueous solution or a molten salt. Specifications such as deposition of pure metal or alloy coatings of any composition are met by selecting materials based on deposition rate, deposition efficiency and throwing power.

Electrochemical Cell

Elements of an electrochemical cell include the container, the melt and the electrodes. The anode and cathode are immersed in the melt in the container. Temperature, electrochemical limits and the atmosphere influence the operation of the cell. When a voltage is applied between the anode and the cathode, electrolysis occurs in the molten salt, and electrodeposition occurs.

Electrodeposition

The anode, or metal to be use for plating, and the cathode, or substrate to be plated, are immersed in a salt medium such as alkali metal halide. Silver (anode) is deposited on jewelry located on the cathode (substrate), for example, in silver electroplating. The metal to be plated dissolves in molten salt, and the solvent facilitates the plating process. The electrical charge (current passed through the solvent for a given time) determines the coating thickness. The uniformity of coating is influenced by the anode-cathode geometry. The coating does not become part of the substrate in electrodeposition; however, at elevated temperatures the coating and substrate interdiffuse with each other.

Electroforming

The coating formed by electroforming is so thick that a free-standing coating can be formed by removing the substrate. An artist can use a mandrel -- a rod made of wax, metal, or another material -- to make a replica of a statue, for example, coat it with gold and drain out the material or dissolve it away. Also, complicated shapes such as beautiful pieces of jewelry can be formed from ductile materials using electroforming techniques.

Protective Layers and Coatings

Types of protective layers and coatings based on electroplating include:

  • metallic
  • multilayered
  • alloy
  • composite
  • conversion
  • anodized
  • electroforming

Metals such as gold and silver, for example, can be used for metallic coatings. Several layers of materials such as copper and nickel are deposited in multilayered coatings. Alloys -- mixture of metals such as tin and lead -- can also be used for coatings. Composites, materials with different ingredients such as cobalt and chromium carbide, are used for specific coating applications. Conversion coatings have oxide, phosphate or chromate surfaces that provide improved corrosion resistance. A metal such as aluminum is used as the anode in anodized coatings, which are widely used in the food packaging and processing industry. Electroforming is a popular technique for jewelry making.

Related Articles

How to Make an Electrode
Bronze Plating Process
Chemicals Used in Gold Plating
How to Purify Gold
Zinc Plating Process
Exhaust Dyeing Process
The Effects of High Temperature on Epoxy
What Are the Uses of Tungsten?
How to Electroplate at Home
How to Prevent Rust With Coatings
The Types of Cells Which Lack a Membrane Bound Nucleus
What Is Inconel?
Methods for Desalination
How to Identify a Gold Bearing Area
How to Make Salt Crystallize
Steel Vs. Galvanized Steel Strength
Metal Coating Method on Plastic
What Are Three Important Parts Needed to Make a Battery?
How to Write the Net Ionic Equation for the Reaction...

Dont Go!

We Have More Great Sciencing Articles!