A Pollution Prevention Guide for Metal Fabricators

A Publication of the Pollution Prevention and Compliance Assistance Program

Metal Fabricators

Industries involved in the manufacture of metal products generate many types of waste, coming from a variety of activities and processes. All steps of the manufacturing process -- machining operations, parts cleaning and stripping, surface treatment, plating, and paint application -- have the potential to produce wastes that are classified as hazardous under federal or state regulations. Even those wastes that are not considered hazardous must be handled properly in order to avoid damage to the environment or to public and worker health. The cost of treating and or disposing of these wastes in a safe manner can be high.

The wastes that a metal fabricating business would have to contend with might include many of the following:

  • spent metalworking fluids
  • acid/alkaline wastes
  • halogenated and non-halogenated solvents
  • abrasives
  • process solutions and rinse-water containing toxic substances
  • contaminated wastewater treatment sludge, still bottoms, etc.
  • empty product containers
  • paint overspray

Whatever the nature and characteristics of the waste may be, it all has one thing in common: All waste represents loss of resources and loss of money.

Businesses throughout the country have implemented waste reduction programs and found that there are many benefits to be gained from such an approach to the management of resources. Reducing the amount of waste your business generates can help you:

  • reduce operating costs
  • reduce waste disposal costs
  • reduce long-term liability
  • help sustain environmental quality
  • improve workplace safety and health
  • project a positive public image

The most effective way to minimize the losses associated with waste is to avoid producing the waste in the first place. This is the concept behind DNREC’s Pollution Prevention and Compliance Program, which has produced this Guide to assist you and others in the metal fabrication business to reduce your losses while at the same time helping to improve the environment.

Getting Started

A comprehensive waste audit is the essential first step in developing a waste reduction strategy. The purpose of the waste audit is to identify all operations that produce waste and the areas where waste may be reduced.

Here are the steps to follow in conducting a waste audit:

  • List all wastes being generated.
  • Identify the composition and source of each waste.
  • Identify options to reduce the generation of these substances, focusing on those waste that are most hazardous and those techniques that are most easily implemented.
  • Compare the technical and economic feasibility of the options identified.
  • Evaluate the results and schedule periodic reviews of the waste reduction program.

Improved Operating Procedures

Improving the company’s operating procedures is often the easiest and least expensive way to reduce waste. No expensive equipment or materials are involved -- only small changes in the way things are done. This includes improvements in housekeeping, inventory control, material handling, and actions taken to prevent spills, leaks, or equipment breakdowns. Here are a few examples of good operating procedures that can reduce waste:

  • Keep storage and work areas clean and well organized, and keep all containers properly labeled.
  • Inspect materials upon delivery, and immediately return unacceptable materials to the supplier.
  • Keep accurate records of raw material usage so that you can measure reductions in use. Mark the purchase date on each container and adopt a “first in, first out”, policy so that older materials are used up before new ones are opened; assign someone to distribute and keep track of raw materials.
  • Practice preventive maintenance to avoid future losses. Conduct periodic inspections of tanks, tank liners, and other equipment; repair malfunctions when they are discovered.
  • Keep all containers covered to prevent evaporation, spillage, or drying out of contents.
  • Keep waste streams separate for reuse, recycling, or treatment. Keep non-hazardous materials from becoming contaminated.
  • Limit bath mixing to trained personnel.
  • Use bench-scale testing for samples rather than in process baths.
  • Install drip trays and splash guards to contain spills and leaks.
  • Inspect plating racks for loose insulation that would cause increased dragout.
  • Use dry cleanup wherever possible to reduce the volume of wastewater.
  • Material Substitution
  • Replacing hazardous materials with less hazardous substitutes will reduce the toxicity of the waste. Look for the least toxic materials available that will meet your needs. When choosing materials, also look for recyclability. Here are some substitutions to consider.
  • Use process chemistries that are treatable or recyclable on site.
  • Use deionized water instead of tap water for process baths and rinsing operations; this will reduce the amount of sludge generated.
  • Replace cyanide and barium salt baths in metals heat treating processes with alternative treatment methods, including the use of sulfate or chloride baths.
  • Use alkaline cleaners instead of solvents in degreasing operations. Some alkaline cleaners may be treated on site and disposed of in the sanitary sewer system (with permission of the POTW).
  • Use less toxic plating solutions. For example, use zinc instead of cadmium, and trivalent chromium instead of hexavalent chromium.
  • Use no-rinse coatings.

Extending Process Bath Life

The lifetime of a plating solution can be prolonged by minimizing losses due to evaporation and slowing the accumulation of impurities. Here are some tips for extending the bath life:

  • Cover bath when not in use to reduce evaporation.
  • Test process, baths for pH, metals, and other indicator parameters to determine when replenishment or treatment is in order. Replenishment (by adding necessary chemicals) or treatment (by filtration, electrolytic dummying, or other methods) can extend the useful life of the bath.
  • Properly design and maintain racks to reduce build-up of corrosion and salt deposits, which will contaminate plating solution.

Reducing Drag-out

Reducing the drag-out from the plating bath into the rinse tank can result in savings in raw materials as well as treatment and disposal costs. Here are some techniques for reducing drag-out:

  • Minimize bath concentrations to the lower end of their operating range. This will save on materials, reduce solution viscosity and dragout, and reduce the toxicity of the bath solutions.
  • Increase the temperature of the bath to reduce both the viscosity and the surface tension of the solution.
  • Use non-ionic wetting agents to reduce solution surface tension.
  • Withdraw work-pieces from tanks slowly to allow maximum drainage back into the process tank.
  • Use air knives or spray rinses above process tanks to rinse excess solution off of work-pieces and into the process bath.
  • Install drainage boards between process tanks and rinse tanks to route drag-out back into the process tank.
  • Use dedicated drag-out tanks after using process baths to capture drag-out.
  • Install rails above process tanks to hang work-piece racks for drainage prior to rinsing.
  • Rack parts properly to maximize drainage.

Conserving Rinse Water

Efficient rinsing techniques can not only save on water usage; they can also improve the quality of the product. Here are some techniques to consider:

  • Install automatic flow controls.
  • Spray rinse the work-pieces as they emerge from the process tank.
  • Install multiple rinse tanks in a counter-current series system.
  • Agitate the rinsing bath either mechanically or with air.

Reducing Paint Wastes

Metal fabricating businesses may generate several types of paint waste, including: cans containing residual paint; waste paint resulting from overspray or from failure of the paint to reach its target; and waste generated by clean-up after a painting operation.

Here are some suggestions for reducing these wastes:

  • Purchase paint in bulk, so as to reduce the number of paint cans requiring disposal. If this is not practical, purchase. the paint in the smallest amount required; this will minimize the amount of residual remaining in the can.
  • Waste associated with paint application can be reduced by
  • Changing the method of application. Roller and flow coating machines and electro coating systems are much more efficient than conventional spray systems.
  • Finding safer substitutes for conventional solvent-based systems. Water-based, radiation-cured, and powder coatings are three systems that eliminate or greatly reduce the use of volatile solvents in the paint application process. They also reduce the amount of paint overspray requiring disposal.
  • Clean-up wastes can be reduced by careful scheduling of the paint operations. Scheduling all batches of the same color to be done on the same day or during the same part of the day can reduce the number of cleanups required. When different colors will be applied on the same day, try to do the lightest colors first and move progressively to the darker colors.

Reusing and Recycling Other Wastes

Good waste reduction plans address all of the waste streams being generated by a particular business or industry. Try to find ways to apply the Three Rs to all of your company’s waste, including such things as waste paper, empty containers, lubricating fluids, etc. Here are some tips for these types of materials:

  • Reuse or recycle excess, off-specification materials and samples taken for quality control testing.
  • Segregate and reuse dust emissions in the production process.
  • Distill waste solvents, and regenerate catalysts.
  • Find as many ways to reuse paper as you can (as note pads, poster paper, etc.).
  • Recycle as many of the company’s waste materials as possible. Corrugated cardboard, computer and office paper, aluminum, ferrous metals, and plastic and glass containers are some commonly recycled items. DNREC’s Pollution Prevention and Compliance Assistance Program (739-3822) may be able to help you find recyclers for various materials.
  • Recycle lube oils.

Getting the Job Done

Accomplishing the goals of a waste reduction program requires the cooperation of every employee of the company. Top management must make a commitment to pollution prevention, but it will be the workers themselves who will make the program succeed.

Management can demonstrate its commitment to waste reduction by:

  • Providing employees with training in waste reduction techniques and practices -- including periodic “refresher courses” to increase employees’ awareness of the importance of waste reduction.
  • Involving the employees in designing and implementing waste reduction measures.
  • Establishing incentives to encourage workers to use waste reduction techniques and to suggest changes in design or operating procedures that would further reduce waste generation.

Following Up

As long as wastes are being produced, there is the potential for waste reduction. Less-polluting materials, equipment, and procedures are constantly being developed, so that wastes that are difficult or costly to control today may be easily eliminated tomorrow. Stay alert for such developments.

Here are some ways to keep the waste reduction program vital:

  • When buying new equipment, look for equipment will minimize both the amount of toxic materials used. and the amount of waste produced.
  • Reassess the company’s operations and waste handling practices periodically with an eye to avoiding the temptation of slipping back into old, more wasteful ways of doing things and to identify additional waste reduction possibilities.
  • Publicize the firm’s commitment to waste reduction. Customers will feel good about doing business with a company that is environmentally responsible.

Sources of Additional Help

This Guide is not intended to be a comprehensive list of all the techniques that could be used to reduce waste in a metal fabrication company. Each facility is unique, with its own challenges and opportunities for minimizing waste; therefore, each waste reduction program will be unique. There are a number of resources available to help Delaware businesses develop and implement programs that meet their individual needs:

  • The Northeast Industrial Waste Exchange may be able to help you find companies that can use your wastes. You can call the Exchange directly at 315-422-6572 and identify yourself as a Delaware business, or call the Pollution Prevention and Compliance Assistance Program.
  • The Delaware Manufacturing Extension Partnership is a private, non-profit corporation which is dedicated to improving the quality, productivity, and profitability of Delaware manufacturers, and to serving as a prime service resource for the state’s new and existing manufacturers. The DEMEP can be reached at (302)283-3133.
  • A Waste Reduction Self-Evaluation Manual has been developed by the Department of Natural Resources and Environmental Control to assist small and medium-sized businesses in implementing waste reduction programs. Copies of the manual can be obtained by calling the Pollution Prevention and Compliance Assistance Program at 739-6400.
  • The Delaware Pollution Prevention and Compliance Assistance Program in the Department of Natural Resources and Environmental Control (302)739-6400 provides technical assistance, information resources, as well as assistance with other services that are available to your business.

Delaware Department of Natural Resources and Environmental Control

This publication is one of a series of pollution prevention guides for various types of businesses. For more information on this and other pollution prevention or waste minimization programs, contact the Department of Natural Resources and Environmental Control at 739-6400.

The Department of Natural Resources and Environmental Control is an equal opportunity employer. No person or group shall be excluded from participation, denied any benefits, or subjected to discrimination on the basis of race, color, national origin, or handicap.

Last Updated: May 28, 2002

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