Metal Finishing is a term that is used to describe many forms of treatments of metals, of countless different types and alloys. Metals have been finished or treated for thousands of years. Early civilizations would create hammered, polished and sanded finishes on a variety of metals such as bronze, copper, gold, silver, and iron. These finishes were applied to jewelry, containers, and weapons.
As time went on the processes and finishes became more sophisticated, as did the equipment and methods to utilize these finishes. Several newer finishes had a much more functional use.
Finishing today encompasses media blasting for metal cleaning and preparation for other finishes, with various elements such as sand, corundum of varied grits. Walnut shells are even used on soft metals. Even commercial diamond media is used on hard metals. These processes are utilized to prepare metals for painting for corrosion protection, solid film lubricants for wear enhancement, and cosmetic, as well as decorative uses. The blasting media is forced through a nozzle at high pressure using compressed air. Another type of finish is achieved by polishing. This method is done by hand or by automation with abrasive wheels of varying grits to achieve the desired finish. High polish is performed employing cloth wheels with polishing compounds applied to obtain the high polish required.
Metal plating is another sophisticated process that has been developed to deposit various types of coatings on metal parts. These layers range from, cadmium, zinc, chromium, gold, silver, copper, to protect, create electrical characteristics, wear enhancement, or create decorative finishes as required. Electro-deposit is applied to the plating processes in a solution where an anode and cathode relationship with the item is created, and the coating is deposited from the plating solution onto the item being plated. There is another process that uses vacuum deposition of a layer onto non-conductive materials such as plastic.
An additional process is anodizing. This process is also performed using electric current, in an acidic solution designed to cause an anodic coating rapidly to be formed on the surface, and to some degree the substrate of the material being anodized. This process is used on aluminum and titanium metal alloys. The type of anodic coating determines the thickness and end use. Many of the coatings are somewhat thin and lend themselves to dyeing in a host of colors for decorative applications, but also act as a protective coating from the elements. One of the anodic processes is defined as hard anodize, and may be applied to a high level of thickness, several thousands of an inch thick. This method has very high hardness and is used for high wear applications, for bearing surfaces as an example. This coating is also used in many marine, salt exposure applications and is very resistant to corrosion.
Solid film lubrication, as discussed earlier, is an example of a coating that can be applied to numerous products. Including lubrication of wear surfaces, a temperature, and corrosion resistant barrier, as well as for friction reduction of mating parts. For instance, manufacturers of metal bellows use this process for wear surfaces of bellows expansion joint and flange interfaces. This application improves both wear and friction reducing attributes.
The continued experimentation and improvement, of these various processes, are ongoing throughout the metal finishing industry. We expect to see new and improved methods, being brought to market, as time continues to go forward. Without metal finishing, many industries would not exist, or the products offered would be much inferior to what is available today.