Nickel plating is a time-consuming process that produces a hard, lustrous finish on metal objects. It involves hazardous materials and strict regulations, but can be a lucrative business. The process involves multiple steps, including cleaning and plating with nickel and chromium. The thickness of the plating can range from 1 mil to 20 mil. The chemical bath used in the process must be carefully dosed, heated, and agitated. Chromium is a known carcinogen and the process is subject to strict regulations. The wastewater produced in the process is considered hazardous waste and must be disposed of accordingly.
Nickel plating is a labor intensive and time consuming process of giving an object a very hard and lustrous metallic finish. A popular process in finishing metal parts on trucks, cars and motorcycles, as well as household fixtures such as faucets and knobs, it is a process where the materials and processes include significant health and environmental risks. It’s not a business to do as a weekend hob, but it can be a lucrative business for those willing to work patiently and meet standards for the safe handling and disposal of the many hazardous materials involved.
Nickel plating produces a hard finish that can be highly polished, leaving a bright and aesthetically pleasing appearance, as well as providing some resistance to rust and corrosion to the object being plated. While some alternative, less hazardous processes, such as powder coating, can produce similar-looking results, they cannot be used on objects that are subject to high temperatures in normal operation, such as motorcycle exhaust pipes or engine pistons.
There are many steps involved in nickel chrome plating. First, the surface to be plated must be thoroughly prepared: it must be chemically and microscopically clean. Mechanical means such as grinding and polishing are used to achieve this state, as well as acid baths to remove any surface contaminants. If there is any foreign material on the surface, it won’t catch the pot.
Nickel-chroming actually consists of at least two separate plating processes: the item is first plated with nickel and then plated with chromium. Also, nickel plates are especially good on copper, so in many plating operations, the surface is first plated with copper. Although much more time consuming, a nickel-chrome over copper plate is extremely durable. After each step of the plating process, the piece must be cleaned and polished, as any surface imperfections will remain visible on the finished piece. Some metals, especially aluminum, require extensive special preparation before they can be plated.
The plating process molecularly bonds very thin layers of nickel and chromium to a metal surface. Thickness can range from approximately 1 mil to 20 mil (1 mil = 0.001 inch or 0.0254 mm.) A human hair is approximately 1 mil, and a household plastic garbage bag is 3 mil thick. While different parts of the process can be modified slightly to speed up the process a bit, you should expect a plating thickness of about 1 mil for every hour of the process. This usually takes place in a chemical bath through which an electric current is passed from an anode to the workpiece, which acts as a cathode. For the nickel plating portion of the process, the anode itself is made of nickel, and as the current is turned on, the nickel slowly leaves the anode and migrates through the chemical bath to the cathode, the workpiece. For the chroming phase, the anode is made of lead and chromium is one of the ingredients of the bath itself, in the form of chromic acid mixed with sulfuric acid and water.
The electroplating chemical bath requires careful attention to detail. The different ingredients must be dosed precisely and the bath itself must be heated for optimal results. Furthermore, to keep the temperature constant throughout the mixture and to continue to refresh the solution in contact with the piece, the bath must be continuously agitated. This agitation is usually accomplished by pumping air through a perforated plastic tube, producing a stream of bubbles, although other means may also be used, such as holding the workpiece or placing a small propeller in the bath.
Many forms of chromium are known carcinogens and the entire nickel-chrome plating process is subject to strict regulations in most jurisdictions. In fact, the regulatory burden imposed by some municipalities effectively amounts to a ban on nickel plating. In jurisdictions where it is permitted, the area where the nickel-chroming process takes place must be adequately ventilated, as chromium is present in the vapors produced in the process and can easily be absorbed through the lungs. Furthermore, not only is the chemical toilet itself considered a hazardous material whose handling is regulated by law, but the wastewater produced in the process of cleaning and rinsing parts and equipment is also considered hazardous waste, as is everything with which it comes contact. This waste cannot simply be flushed down the plumbing; must be contained and disposed of according to regulations.
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