Manufacturing A Bright Finish
As the business climate changes, manufacturers continue to look for innovative ways to get their products to market. Today, we not only look for innovation, we look to reduce our impact on the environment. This fact is evident when comparing two methods of producing a bright finish for the automotive aluminum wheel industry. Traditional chrome plating has been around since the early 1920’s and has been a manufacturing staple for many years. With the introduction of the Clean Air Act Amendments of 1990 and the more recent implementation of the 2003 Restriction of Hazardous Substances in Europe, chrome plating will not be viable means in the future. As technology has progressed, Physical Vapor Deposition (PVD) has emerged as a real solution. PVD is bright, durable and environmentally friendly.
Chrome Plating VERSUS Physical Vapor Deposition
Metal Deposition at its simplest form can be broken down into two technologies: Aqueous Processes and Dry Processes.
Chrome Plating
Chrome Plating is an aqueous process as highlighted by the figure below:
The environmental impacts of this type of deposition can be grouped into the three following categories:
Air (to atmosphere) – In order to control hexavalent chromium emissions from the chrome plating process, facilities use chemical fume suppressants, mechanical fume suppressants, or add-on air pollution control devices such as air scrubbers or Hepa filters.
Water (to sewer) – Some facilities have permits for onsite treatment of hazardous waste. These units are used for PH adjustment, destruction of cyanide, precipitation of heavy metal to acceptable levels, and reduction of hexavalent chromium before discharging the waste stream into the sewers.
Hazardous Waste (to landfill) – This can be generated in solid or liquid form and is required to be stored in closed containers before being shipped to a landfill or treatment unit. The facility is required to retain all manifests and comply with state requirements. Examples of this waste stream are dust and shavings from the abrasive blasting and polishing operations, and waste cakes from filter presses serving the waste stream.
Energy consumption is also an environmental issue. Additional energy is continually being consumed to keep pollutants at acceptable levels. This is not energy required to provide the metal deposition, but rather control its side effects.
Along with being harmful to our environment, chrome plating is also dangerous work. Chromium plating baths consist of acid solutions which bubble while releasing hydrogen and oxygen. These bubbles create mists which can be inhaled. Caustic chemicals can reach the worker through spills or splashing.
Physical Vapor Deposition (PVD)
PVD is a dry process as highlighted by the figure below:
PVD does not have any negative effects on our environment.
Air – Argon is colorless, odorless, and tasteless in both its gaseous and liquid forms. Argon is inert and cannot form hazardous compounds. It is present in our atmosphere at .94%
Water – not used
Hazardous Waste – none
Metal ions that do not attach themselves to the aluminum substrate are considered overspray. Overspray is collected by a simple vacuum cleaner with a paper filter. The metal itself is not considered a hazardous waste stream.
In addition to being efficient, the actual amount of metal applied to a PVD coated aluminum wheel is measured in Angstroms. This leads to a general weight savings per wheel of .5#(226 grams). This weight savings equates to fuel efficiency.
Comparing the two technologies, it is clear that PVD is truly a green technology. As manufactures adopt this application method it will become the new norm. Just as the environmental regulations during the 1990’s provided grounds for powder coating to grow in a market of liquid applicators, PVD has made its way through the vast field of plating. The future for PVD is bright.
