Powder Coating has been the go-to process for metal finishing for decades. It’s versatile, cost-effective, and produces beautiful results every time. However, some industries require additional corrosion resistance that powder coating alone can’t provide.
In these cases, manufacturers use an electrochemical finish (also known as E-Coating) before applying a final coat of powder. E-coating is an electrochemical process that produces a durable and porous oxide layer on metal surfaces using electrolytic oxidation and a chemical process called anodization.
Anodizing creates porous alumina areas on the material’s surface, which serves as a sacrificial layer during subsequent mechanical or chemical surface finishing processes, like etching, sandblasting or grinding, etc., depending upon the application.
This article explores six reasons you should use e-coating before powder coating.
E-Coat Development
Companies have used electrochemical processes to create durable and protective metal coating for decades. The earliest and most common of these finishing processes is electroplating, which uses a voltage to electrochemically deposit a layer of a different metal onto a base metal.
For producing an appropriate surface for powder coating, however, there was a need to develop a different electrochemical process.
Anodizing, developed in the 1950s, is an electrochemical process that creates a porous, corrosion-resistant surface on meta that prevents corrosion in aluminum aircraft. Electrochemical processes use electrical charges to create chemical reactions in metals.
In an electrochemical cell, applying a voltage to a solution containing the metal to be coated and electrolyte, a chemical that conducts electricity. The electrical current causes metal ions to be oxidized (lose electrons), forming metal ions in the solution and creating chemical changes in the metal surfaces and the solution.
Anodizing creates porous alumina areas on the surface of the metal, which serves as a sacrificial layer during subsequent mechanical or chemical surface finishing processes, like etching, sandblasting or grinding, etc., depending upon the application.
Cost Efficiency
An e-coating occurs in a single tank with minimal waste and no dust, making it ideal for clean-room environments. E-coat costs vary based on the size and type of metal being coated, the volume of metal being coated, the desired thickness of the coating, and the complexity of the coating.
Produces Superior Corrosion Resistance
Powder coating produces a high-quality finish but doesn’t provide e-coating’s superior corrosion resistance. An electrochemical process creates a more chemically stable oxide layer than a thermal (i.e., bake or flame) process.
The higher chemical stability means the oxide layer formed during anodizing resists chemical attacks longer than a thermal oxide layer.
Enhances Surface Adhesion
The porous surface created by e-coating is perfect for adhesion. It’s often used to enhance the adhesion between different materials. Whether taking two different materials and adhering them to one another or taking two different surfaces and adhering the coating to both, e-coating is perfect for the job.
The porous surface created by the anodizing process makes it easy for the powder to adhere to the surface, creating a smooth surface, and making it easy for the topcoat to flow and conform to the part’s shape.
Increases Coating Durability & Performance
The porous surface created by e-coating is advantageous for adhesion, durability, and performance. It’s a dense but porous surface proven to withstand various mechanical and environmental conditions.
Because e-coating creates a dense, tight oxide layer, it prevents the underlying metal from being attacked or corrupted. As a result, the coating adhering to the oxide layer will last longer and perform better than a coating applied to untreated metal.
Reduces the Need for Final Coating Cycles
Using powder coating as the final coating on a part will most likely require a final coating process to protect it from the environment, called a topcoat or clear coat.
If the part is e-coated first, then with powder, an additional clear coat may not be necessary. The porous surface created by anodizing is more durable than a surface with no protection. As a result, the coating adhering to the porous surface is more durable than a coating adhering to a non-prepared surface. The additional durability of the coating may reduce the need for a topcoat, saving time and money.
Summary
For decades, we have used electrochemical processes to create a durable and protective metal coating. The earliest and most common of these finishing processes is electroplating, which uses a voltage to electrochemically deposit a layer of a different metal onto a base metal, such as applying gold onto silver jewelry.
Electrochemical processes use electrical charges to create chemical reactions in metals. In an electrochemical cell, applying a voltage to a solution containing the metal to be coated and electrolyte, a chemical that conducts electricity. The electrical current causes metal ions to be oxidized (lose electrons), forming metal ions in solution. The reduced metal forms metal atoms as the current flow from the solution to the metal.
These reactions create chemical changes in the metal surfaces and the solution. Anodizing creates porous alumina areas on the surface of the metal, which serves as a sacrificial layer during subsequent mechanical or chemical surface finishing processes, like etching, sandblasting or grinding, etc., depending upon the application.
These reasons are why you should use e-coating before powder coating. It’s a cost-effective process that can enhance your product’s durability and performance.