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Anodizing is an electrolytic passivation process designed to increase the thickness of the naturally occurring oxide layer on the surface of metal materials. Anodizing is generally used to improve the corrosion resistance of the treated material; it can also improve its dielectric properties and aesthetics. A variety of metals can be anodized, such as aluminum, magnesium, zinc, titanium, niobium, and tantalum. The anodizing process relies on a very specific chemical-electrical reaction. As such, anodizing requires very specific chemicals to produce the desired results. Prior to being anodizing, the metal workpiece must be cleaned in a hot soak or a solvent bath, usually using sodium hydroxide, ammonium bifluoride, or a mix of acids. For the anodizing process itself, direct current voltage is applied to an acid solution. Depending on the metal being anodized, the process being used, and the desired results, the acid used varies, as does its concentration in the solution. Most common are chromic acid (used for Type I anodizing), sulfuric acid (Type II and Type III anodizing), and organic acids, such as malic acid. Phosphoric acid, borate, or tartrate baths can also be used to provide unique coating results. Numerous other chemicals can also be added in the anodizing process, such as dyes for coloration, additives to reduce the end product’s coefficient of friction, ingredients to prevent burning of the material, and others.
- Sanford Process is an industry leader in the global hard anodizing market. The company provides a variety of high quality anodizing supplies and equipment.