Metal plating refers to coating a substrate with a metal such as cadmium, zinc, gold, or silver. Cadmium plating is very common for industrial processes as it makes other metals resistant to corrosion. It can be done on steel, iron, aluminum, and brass to protect them from corrosion. It also offers other benefits for substrates such as greater lubricity, better electric conductivity, and more solderability.
Due to these benefits, cadmium plating is very popular in industries such as aerospace, electrical, mining, defense, and automotive. Cadmium coatings can be applied using either electroplating or mechanical processes.
The Cadmium Plating Process
Mechanical or Barrel Plating –
The process involves use of a barrel where substrates and other substances like cadmium powder, propriety chemicals, and glass beads rotate inside it. The barrel rotation mechanically coats the metal items with cadmium. The mechanical process is suitable for small metal items such as clips or screws.
Electroplating refers to coating a metal on a substrate with the help of electrical currents. The main substances required for this metal plating process are cadmium salts to form a powerful electrolyte solution. When an electrical current runs through the solution, cadmium coats the substrate. Cadmium electroplating is suitable for delicate or large substrates.
Vacuum Deposition –
Another method for cadmium plating is through heating the metal in order to vaporize it. The heating is done in a vacuum. Once this process is complete, condensed cadmium atoms deposit on the substrate. The cadmium coating achieved through this methods is thin and of a very good quality. The ions in the vacuum also help to enhance the properties of the cadmium coating. Cadmium plating through the vacuum method is mostly used for rotor parts in helicopters, parts of aircrafts, and steel parts with high tensile strength.
The Preparation Process
The preparation process for metal plating can consist of one or more stages. Before any kind of metal plating can occur, it is important to clean the substrate thoroughly. Without cleaning the substrate, the coating is unlikely to be of a high quality. The contaminants can even impact the bonding process of the coating material and the substrate.
The substance needed for the cleaning step is a chemical solution at a high boiling point. The heat in contact with the cool substrate surface causes the contaminants to separate from the metal. Through the process, all unwanted materials from the metal separate; making it ready for the coating process.
In some cases of metal plating, sandblasting may be used after the chemical-cleaning process. Aluminum oxide in rough powder form may be used to make the metal surface more conducive to the coating process.
The Rinsing and Strengthening Process
Water and chemicals are used for completing this stage of the metal plating. After the metal plating is complete, the substrates are rinsed with water to remove extra chemicals. Depending on the metal plating (cadmium or another metal), the substrates may be dipped into special compounds to strengthen their corrosive properties. If needed, the newly-coated substrates may be rinsed once more with hot water.
Choosing Cadmium Plating
The process of cadmium plating is best decided based on the substrates, industry, and the final application. Rack cadmium plating may be more suitable for some items while for others electroplating may be more beneficial. The right service provider can help you decide on the most beneficial cadmium plating process for your requirements.
Cadmium offers better protection from corrosion than any other coating material. It also corrodes first in case the protective layer is damaged (sacrificial coating) and the substrate is exposed. Such a possibility is not very likely with quality coating works, but sacrificial coatings means additional protection for substrates. Even in cases of scratches on the metal surface, cadmium plating can continue to protect the substrate from corrosion and other types of damage.
Cadmium is at times preferred over zinc plating due to concerns with toxicity and subsequent environment damage. But if the service providers take proper measures to tackle the waste from cadmium plating, there is no reason not to benefit from it. In case of concerns, it is best to ask the prospective service provider about disposal measures in use.
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