METAL FINISHING INDUSTRY

These days everyone doing pollution prevention assistance seems interested in helping the metal finishing industry; ever wonder why? Metal finishing, when taken as a whole, is one of the largest users of many toxics chemicals in the country. Electroplating alone is the second largest end user of nickel and nickel compounds, and the third largest end user of cadmium and cadmium compounds. Electroplating also accounts for a substantial amount of chromium use in the United States. In other words, this industry is responsible for managing large amounts of hazardous materials (Davis 1994).
Many industries use metal finishing in their manufacturing processes including automotive, electronics, aerospace, hardware, jewelry, heavy equipment, appliances, tires, and telecommunications. Figure 1 shows the percent of markets served by metal finishers in 1992.
Why is metal finishing so prevalent? Without metal finishing, products made from metals would last only a fraction of their present lifespan because of corrosion and wear. Finishing is also used to enhance electrical properties, to form and shape components, and to enhance the bonding of adhesives or organic coatings. Sometimes the finishes are used to meet consumer demand for a decorative appearance.
Overall, metal finishing alters the surface of metal products to enhance: Corrosion resistance , Wear resistance , Electrical conductivity , Electrical resistance , Reflectivity and appearance (e.g., brightness or color), Torque tolerance , Solderability , Tarnish resistance , Chemical resistance , Ability to bond to rubber (e.g., vulcanizing) and Hardness
Metal finishers use a variety of materials and processes to clean, etch, and plate metallic and non-metallic surfaces to create a workpiece that has the desired surface characteristics. Electrolytic plating, electroless plating, and chemical and electrochemical conversion processes are typically used in the industry. Typical supporting processes can include degreasing, cleaning, pickling, etching, and/or polishing.
Some of the materials used in metal finishing are solvents and surfactants for cleaning, acids and bases for etching, and solutions of metal salts for plating the finish onto the substrate. Figure 2 presents an overview of the fabricated metal products manufacturing process and shows the types of emissions and wastes that are generated during production.