Environmental groups are concerned by the electroplating process's byproducts. While chromium electroplating results in excellent resistance to corrosion, it also produces carcinogens. Carcinogens are substances that can cause cancer in living tissue. Hexavalent chromium, which is used in products ranging from stainless steel to wood preservers, to textile dyes is an especially potent lung carcinogen. As a result, an increasing number of alternatives to chromium and to electroplating have arisen.
The thermal spray method is sometimes referred to as thermal coating. Thermal spraying is blanket term for a group of processes. In general though, these processes, involve the deposit of molten or semi-molten materials onto another surface to form a coating. This is most commonly done with metals, but can be done with nonmetals as well. The technique is used worldwide and generates more than 2 billion dollars in revenue each year.
Electro-spark deposition is a relatively new process, and thus is not as widely known as thermal spray. However, its advantage over thermal spray or electroplating is that it carries a reduced risk of discoloration or burn-through due to heat. Essentially, electro-plating uses a moving electrode that uses short, high-current electrical pulses to bond metals. The process does not produce hazardous wastes, can be used to plate objects with complex shapes and is easily automated as well.
Electro-less nickel coatings are also a common alternative to chromium electroplating. It is especially useful where the resultant object will need to have a very high melting point. In fields such as aerospace and electronics, electro-less nickel coatings are common. Electro-less nickel plating is a chemical process that depends upon a reducing agent to be successful. Sodium hypophosphate is one example of a reducing agent. The agent reacts with metal ions, depositing them onto the metal being plated.
There are many alternatives to chromium electroplating in various stages of development. Some of these include physical vapor deposition, laser cladding, explosive bonding or more simply, the use of nickel-cobalt alloys or tin in chromium's place.