Metals such as steel, aluminum, and iron are used for a variety of structural components, mechanisms, enclosures, decorative parts, and other uses. These metals can oxidize or corrode when exposed to environmental effects such as rain, wind, or chemicals. To increase the working life of these components, designers and fabricators often add a coating to act as a barrier between the metal base and the environment.
Choosing a Metal Coating Process
Fabricators have many options when considering what sort of coating is most appropriate for a specific application. Some of the factors to consider when selecting a coating method include:
- Environment – Environmental variables could include wind/rain/ice from outdoor installations, salt water near ocean installations, physical stress due to applied loads, and exposure to chemicals that could degrade the coating.
- Service Life – Components that require a long service life with minimal maintenance require coating processes that can withstand environmental effects for a long period of time.
- Cost – Different coating processes have a range of costs associated with them. Engineers have to balance the design requirements with the process costs to select a process that is cost effective for the specific application.
By understanding the working environment of the part, engineers can assess the pros and cons of available coating processes.
Types of Metal Coating Processes
Some of the most widely used metal coating processes include:
- Paint – Paint is an inexpensive coating method that can quickly protect metal parts. Paint can be applied by brush or with a sprayer and dries quickly. However, paint coatings can chip easily and colors can fade due to exposure to the sun. Painted parts can be re-painted as needed to maintain appearance and coverage.
- Powder Coating – Powder coating is a polyester or epoxy powder that is applied to a metal part via an electrostatic charge and then heated to melt and cure the powder into a homogeneous coating. Powder coating is more durable and long lasting than standard paint, but it more expensive. Powder coatings can be created in a wide range of colors, like paint.
- Galvanization – Galvanization involves the application of a thin layer of zinc to the surface of a metal part. Galvanized parts are generally a dull gray color, but some colored galvanization processes are available. The zinc metallurgically bonds with the base metal, creating a coating that will not chip or peel.
- Electroplating – Electroplating uses an electrical current to deposit a thin layer of metal from a solution onto a metal part. Copper, silver, gold, and other metals can be electroplated onto metal parts to improve their appearance, provide resistance to environmental effects, or improve electrical conductivity.
Metal coating processes help to extend the working life of a variety of metal parts that would experience degradation if exposed to environmental effects without a protective coating.
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