The purpose of the roundtable was for participants to share pollution prevention experiences, identify challenges to the implementation of pollution prevention approaches, discuss sources of information and routes of communication, and develop recommendations for efforts to help disseminate essential information and expedite the adoption of alternative technologies.

The roundtable meeting, and subsequently this report, address issues only in the metal plating sector of the metal finishing industry — that is, the application of a metal coating onto a metal part (metal deposition technologies). Metal finishing also includes: the application of paint and related materials onto metal (organic finishing technologies); finishing methods in which the "plated" materials interact with and physically change the make-up of the metal part — anodizing, phosphating, and chromating — (conversion technologies); and subtractive processes that involve the removal of metal from the metal part either through physical action or chemical reaction (removal technologies). Many companies that perform metal finishing operations offer many of these services. However, these technologies were not discussed at the meeting and, therefore, are not addressed in the report. Additionally, activities associated with electroplating printed circuit boards are not included.

This report includes an overview of current and emerging pollution prevention practices and projects at metal plating facilities in the Northwest, and a summary of roundtable discussions, including:

• Pollution prevention approaches platers are interested in implementing;

• Information metal platers need in order to make decisions regarding the incorporation of new pollution prevention approaches; and

• The sources and resources metal platers use — and fail to use — to obtain technical information.

At the conclusion of the meeting, metal platers developed a list of recommendations for future activities that would encourage the transfer of information and the further adoption of pollution prevention approaches. These recommendations are summarized at the end of the report.

Appendix A provides a list of roundtable participants, Appendix B provides an overview of the industry and the primary metal plating processes, and Appendix C includes the primary chemicals used in metal plating that are of environmental concern.

Pollution Prevention Activities and Projects
The following information was compiled from studying a number of pollution prevention plans and annual progress reports submitted to the Washington Department of Ecology between 1991 and 1995, and through subsequent conversations with employees at several metal plating shops whose plans were reviewed. It is important to note that many pollution prevention approaches available to metal platers are not discussed in the section below because they were implemented prior to 1991 or because they were not identified as being implemented in any of the companies studied. Nonetheless, the information below provides a general overview of the types of pollution prevention techniques that are feasible. These projects are loosely organized in the order of the typical process flow, which is discussed in Appendix B.

• Parts Degreasing/Cleaning Projects— One of the most widespread pollution prevention projects implemented at metal plating facilities is the replacement of vapor degreasers, typically using trichloroethylene (TCE) or 1,1,1, trichloroethane (TCA), with aqueous or semi-aqueous based cleaning systems. In Washington, changes in cleaning method largely began in the early 1990s. In most cases, platers started by reducing their vapor degreaser use and cleaning some of their parts in a new aqueous or semi-aqueous cleaning tank. If the company found the cleaner was acceptable, the vapor degreaser was phased out completely. If it was not acceptable, the company typically tried another cleaning solution or, in several cases, went back to using the vapor degreaser.

  The aqueous cleaners are typically alkaline, detergent-based solutions, and are often heated and possibly agitated to provide effective cleaning capabilities. Semi-aqueous cleaners consist of an organic solvent, such as terpenes or glycol ethers, in combination with water. In most cases, a surfactant is added as well. Semi-aqueous cleaners are used as emulsions in water or in concentrated form. Both types typically require a post-cleaning rinse.

  Aqueous and semi-aqueous cleaners do not always remove dirt and grease as quickly or effectively as TCE or TCA. Both alternatives may also require additional drying time once a part is cleaned. These disadvantages have resulted in resistance in using alternative cleaning approaches by both production workers and line managers. Most shops have determined that these disadvantages are outweighed by the benefits of reducing costs, regulatory burdens, and potential future liabilities.

  One problem that metal platers are having when using aqueous cleaners is the increase in water discharges and, therefore, water treatment requirements. Platers are interested in further research being done to find effective ways to recover alkaline degreasing solutions in a way that removes contaminants without removing components of the solution that make the cleaning step work.

• Cyanide-Containing Bath Projects — Cyanide pollution prevention projects have been pursued by companies in two areas: for copper plating baths and for reverse copper stripping baths, both of which traditionally contain cyanide compounds. These projects’ primary advantages are a reduction in cyanide in the wastewater stream and the reduction of cyanide-containing sludge, which must be disposed of as a hazardous waste. These types of projects have been done in a small portion of the Northwest metal plating shops, with the identified projects beginning in 1992. Several companies that attempted to use a non-cyanide plating process or reverse copper strip were not able to successfully implement the alternative, and currently are using the cyanide-based copper processes.

  The non-cyanide plating process is alkaline-based. The stripping alternative identified is an electrolytic stripping process. One reason for the limited implementation of non-cyanide processes in shops is that they require much better control of bath conditions to work properly, including being more sensitive to impurities, thereby increasing operating costs and requiring more highly trained production workers. In addition, the non-cyanide stripping alternatives tend to be slower than the cyanide-based processes. Since stripping is being used to rework a defective or out of specification part, speed is important.

  Although zinc-chloride baths have also been substituted for zinc-cyanide baths in a number of facilities across the country, none of the Northwest companies studied reported any actions being taken in this area.

• Chromium-Containing Bath Projects — Most companies using chromium-plating baths now use a chrome emission suppressent in their baths. These are chemical additives that reduce the evolution of hexavalent chromium from the bath. In some areas, such as the Puget Sound, air regulations require the use of these suppressents.

  Substitutions for chrome plating were found at one facility studied. The company has installed a nickel-tungsten-silicon-carbide plating bath to replace its hard chrome plating line. The alternative has the advantages of a higher efficiency than conventional chrome plating, and eliminates the emissions and worker exposures related to hexavalent chromium. Disadvantages include difficulty in stripping the alternative plate for "spot" repairs or rework, and the high expense of the tungsten compound. Because nickel and tungsten are both regulated and linked to negative health effects, the change does not eliminate concerns about the environmental impact of the process. To date, the company has only used the alternative process for research and development applications and limited customer tests. The company hopes to be using the process commercially in 1996, and eventually completely eliminate the chromium plating process.

  Another project related to chrome that was implemented in 1993 was the use of an ion exchange column to process/purify a company’s four chrome plating baths. The ion exchange column removes heavy metal impurities such as iron, copper, and nickel from the chrome baths, which reduce the efficiency of the baths over time. The ion exchange system is used once to twice a year to process the baths, giving them a theoretically infinite bath life. In the two years the ion exchange unit has been in use, the baths have not been dumped and the original resin is still being used in the ion exchange columns. Eventually, the resin in the ion exchange column will need to be regenerated or disposed of, which will result in a waste stream and associated disposal costs.

• Cadmium-Containing Bath Projects — One company studied replaced its cadmium-cyanide barrel plating process with a nickel-zinc alloy process. This was done in 1992 at the request of a customer (i.e. the change was driven by customer specification requirements). The nickel-zinc alloy plating process is still in full-scale use at the company.

  The nickel-zinc process has the advantage of eliminating the more extensive treatment of waste required for cadmium and cyanide, and reducing worker exposure to these compounds, which are know to have greater health risks. Some disadvantages of the nickel-zinc alternative are its higher chemical and operating costs. Nickel-zinc is not generally as corrosion resistant as cadmium, but has been shown to have comparable corrosion protection to steel and other ferrous metals in marine environments, the application originally specified by the customer that required the nickel-zinc process.

• General Bath Life Extension Projects — A number of companies have installed recirculating lines with filters on their process baths to remove impurities on a continual basis. These filter systems are relatively inexpensive and can increase the useful life of the baths significantly. However, the systems generate a new waste — spent filter cartridges. Depending on the bath being filtered, the spent filters may be classified as a hazardous waste.

  The lives of some baths have been extended by using electrolytic regeneration on the bath. In this process, metal impurities in the bath are plated onto a cathode inserted in the bath. This may be done on a periodic or continuous basis.

• Plating Bath Drag-Out Reduction Projects — Drag-out reduction projects are very common at metal plating shops in the Northwest. Drag-out occurs when plating bath chemicals are lost from a plating bath because they are caught in or adhered to a part being removed from the bath. Drag-out reduction projects have been widely implemented because they require minimal capital investment or increase in operator capabilities. Drag-out techniques used at companies include increasing the length of time parts are held over plating tanks to drain and orienting part racks to improve drainage. Typically, drain boards have been installed to catch drips and return them to the plating bath.

• Rinsing Baths/Systems Projects — A number of companies have installed double, and sometimes triple, countercurrent flow rinse systems to reduce water usage. In some cases, these systems were installed as early as the mid-1980s. Countercurrent rinsing involves arranging rinse tanks so that a part is rinsed in progressively cleaner rinse tanks. The cleanest rinse tank is the only one that has fresh water added; each subsequent tank is fed by the next cleaner tank in line. The advantage of this approach is greatly reduced water usage (each additional rinse tank in the train typically reduces water usage for the line by a factor of 10) and wastewater volume. The disadvantages are the increased capital costs and space required in the facility.

  A limited number of companies have implemented more sophisticated rinsewater control systems in the 1990s that reduce water usage and discharges even further. These systems include flow restricters to further reduce make-up water flows and the use of conductivity meters to control when make-up water is needed based on ion concentrations in the rinse tanks.

• A computerized tracking system for all chemicals used in combination with an internal company material exchange program — This approach has been used at larger companies to reduce new purchases by requiring employees to check the existing computerized inventory to see if the chemical they need is already available as surplus in a different building or department, and whether it is an approved purchase. These systems can simplify regulatory reporting, however, they require a large initial investment in money and time.

• External materials exchange programs — A number of companies have taken advantage of regionally operated materials exchange programs to locate other companies that can use a waste as a feed stream. When successful, this approach takes the waste material out of the regulatory system, eliminating associated management costs.

• Proper segregation of wastes — By not combining nonhazardous wastes with hazardous wastes, the volume required for disposal can be reduced. One example is separating hazardous and nonhazardous spent filters to reduce hazardous filter disposal volume.

• Increased quality assurance and control to reduce rework — Some companies have been successful in minimizing the number of parts that need to be reworked. Reworking typically involves stripping and replating, and is very waste-intensive and expensive. Companies have minimized rework through better training and, in some cases, implementing total quality management programs.

There was limited interest among metal platers at the meeting for having access to information on new technologies from Boeing, the national laboratories, and Concurrent Technologies Corporation (CTC). Some metal plating companies, especially those that contract with Boeing, rely on Boeing to test the economic feasibility and effectiveness of a new product or process before trying it themselves. Often, this is because the shops are required to meet certain specifications, which Boeing dictates in its contracts. For information on technologies Boeing has tested or is currently testing, platers should contact Earl Groshart, Boeing Defense and Space Group (see Appendix A).

In addition, several metal platers at the meeting said having access to technologies evaluated by the national laboratories and CTC would be valuable, and would help them make decisions regarding the implementation of these processes.