News | November 5, 1999

Chrome Plating Device Eliminates Emissions

Source: Responsible Alternatives, Inc.
Chrome Plating Device Eliminates Emissions

The Emission Elimination Device (EED), formerly known as the Merlin Cover, is a patented process that encloses a process tank while chrome plating is being conducted. The EED incorporates strategically located and appropriately sized membrane(s), which allow for free passage of gases while effectively blocking escape of water vapor and chemical mist. The EED is a stand-alone, self-contained unit requiring no supplementary equipment (e.g. blower) or exhaust to outside the facility.

During Hard Chromium electroplating, a number of by–products are generated, namely hydrogen gas, oxygen gas, water vapor and chromic acid mist. The hydrogen and oxygen gases are generated as a by–product of the electrolytic reaction during chromium plating. The Chromic Acid Mist is generated because of the bursting action of hydrogen and oxygen gases at the surface of the plating solution. In conventional ventilation systems, these mist particles are carried away by blowing air across the tank. In addition, since the tank is open to the atmosphere, stray air currents add to the mobility of these particles. In the absence of such air movement, these mist particles will rise and then fall back into the solution because of gravity.

The Emission Elimination Device

For a chromium electroplating tank equipped with EED gases generated during the chromium plating operation escape through the patented membrane on the EED Water Vapor condenses on the inside walls and top of the enclosure. The condensate runs back into the plating solution. Chromium Mist, being heaviest of all by–products and because of the absence of any significant air movement, rises to a limited height and then also falls back into the plating solution. The denser air, caused by the presence of water vapor mist, further reduces upward mobility of the chromium mist particles. In addition, the water vapor mist and droplets of condensed water provide scrubbing of the air inside the EED. In setups where chromium mist extends to the height of buss bars, the water droplets keep chromic acid off the buss bars, extending their life and those of other components of the plating system.

Design and Installation

An adapter is affixed to the top of the plating tank walls with appropriately placed and properly sealed openings for buss bar, plumbing, and electrical conduits, etc. A hinged hood, with counter weights or other mechanical means of opening, is then placed on top of the adapter. A deformable sealing gasket material (compatible with process chemicals) is placed between the tank wall and adapter as well as between the hood and the adapter. An evacuation process is also incorporated into the system as a means of removing any mists or fumes that remain under the hood after the plating process is completed. Gases from the evacuation are exhausted through a filter.

A diagram of the Chrome Plating Emission Elimination Device

The EED Plating Process

Parts to be plated are placed on the buss bars. The contacts must be cleaned and secured to avoid any sparking during plating. After the cover is closed and secured, the rectifier is turned on and the interlocks automatically engage to secure the access door. Interlocks ensure that the door is not opened while plating is being conducted in the tank. When the rectifier is turned off, the evacuation unit automatically turns on and the evacuation unit must be run for its specified period (approximately 1- 5 minutes, per manufacturer's recommendation). The process is automatic.

EED Advantages

There are many advantages to using the EED, not least of which is safety. Tanks are turned off during start–up, preventing arcing and reducing the chance of hydrogen explosion. In the unlikely event of an explosion, the EED shields the operator from the splashing solution. The unit's design is simple — there are no exhaust hoods, ducto work or fume scrubbers or fans, reducing the number of working parts.

Additionally, an effluent control for treating fume scrubber solutions is not required, which means less press/dry time. Because the exhaust hoods, ducting and scrubber equipment are eliminated, more floor space is available for additional equipment and additional costs for materials and labor to maintain scrubber systems are eliminated. Noise reduction, significant cost savings, and water and energy savings round out the many advantages to using the EED in chrome plating applications.

The Emission Elimination Device promises to save time, energy and costs for chrome plating applications.

Information for this article was supplied by Responsible Alternatives, Inc., 4027 Colonel Glenn Hwy, Dayton, OH 45431-1672; phone: (937) 253-4789.

Edited by Marie Pompili