Improving Air Quality in Your Community
Outdoor Air - Industry, Business, and Home: Metal Operations
Note: EPA no longer updates this information, but it may be useful as a reference or resource.Additional Information
Tools and Calculators
You can help metal operations owners and operators reduce emissions of hazardous air pollutants (HAPs), volatile organic compounds (VOC), and particle pollution that may affect shop employees, their families, customers, and the community by encouraging metal operations owners and operators to conduct these activities:
- Use reformulated materials
- Reduce evaporative emissions
- Change cleaning procedures
- Recycle materials
- Change processes
- Upgrade equipment
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Use Reformulated Materials
How?- Choose cleaners and degreasers such as waterborne cleaners that have a lower hazardous air pollutant and volatile organic compound content.
- Use precoated or primed materials that do not require any additional lubrication.
- Use less volatile metalworking fluids to reduce vaporizing in heat treating.
- Reduces emissions.
- An aerospace manufacturer replaced 1,1,1-trichloroethylene and methyl ethyl ketone cleaning solvent with non-toxic cleaner for hand-wiping operations. Workers prefer this cleaner because it is more efficient and leaves less residue. The change reduced toxic emissions by thousands of pounds and saves $250,000 per year (Pacific Northwest Pollution Prevention Resource Center).
- One shop used a stamping lubricant that can remain on the piece until the annealing process. This resulted in savings of $12,000 from reduced disposal, raw material, and labor costs. Waste was reduced from 30,000 pounds in 1982 to 12,000 pounds in 1986. Working conditions also improved by removing vapors associated with the old cleaning process (EPA).
- Training employees to use new materials.
- SAGE
- Fact sheet on alternatives to cleaners and solvents.
- See pages 67-69 of EPA's Sector Notebook Project: Fabricated Metal Products (PDF) (156 pp, 1.6 MB) for more case studies.
Reduce Evaporative Emissions
How?- Securely cover all containers to reduce the chance of spills when transferring materials.
- Use funnels or pumps to avoid spills when dispensing materials.
- Only open air-tight containers when adding or dispensing liquids. This minimizes evaporative emissions and waste.
- Switch to solvents that evaporate more slowly.
- Reduce the amount of time that the metal and metalworking fluids are exposed to the air during cleaning, melting, and die casting.
- Reduces emissions.
- A metal precision casting company switched to a citrus-based solvent for cleaning patterns used to make molds. This reduced the company's fugitive emissions by over 18,000 pounds a year (Pacific Northwest Pollution Prevention Resource Center).
- Reduces the amount of solvent and other materials purchased.
- Capital costs for any new equipment necessary.
- See page 70 of EPA's Sector Notebook Project: Fabricated Metal Products (PDF) (156 pp, 1.6 MB) for more case studies.
Change Cleaning Procedures
How?- "Clean as you go" to reduce the amount of solvent needed for removing heavy build-up.
- Use mechanical cleaning such as scraping or wiping before using solvents.
- Reuse cleaning solution or solvent. Use dirty solvent for initial cleaning, then follow with clean solvent.
- Switch to a water-based cleaning system like an ultrasonic cleaner, manual parts washer, automatic spray equipment, or baths with agitation.
- Reduce storage time between metalworking and finishing to offset the need for rust-inhibiting oils.
- By switching to a water-based parts cleaning system, shops could save $12,600 and reduce emissions by as much as 90% (Pacific Northwest Pollution Prevention Resource Center).
- Switching to a citrus-based solvent for cleaning metal casting patterns results in reduced emissions, and reduced solvent cost.
- One shop used a mechanical rotating brush machine that used pumice to scrub copper instead of cleaning with ammonium persulfate, phosphoric acid, or sulfuric acid. Capital cost: $59,000. Annual savings: >$15,000. Payback period: 3 years. Waste reduction: 100% (EPA).
- Capital costs for any new equipment necessary.
- Training employees to use new procedures.
- Case studies and information on cleaning procedures: Pacific Northwest Pollution Prevention Resource Center has more information on cleaning procedures as well as case studies.
Recycle Materials
How?- Use an on-site distillation unit to clean dirty cleaning liquid. This makes the solvent available for reuse in the production process.
- In metal casting, collect and recycle the dust from furnaces and curing ovens by using pyromettalurgical treatments, rotary kilns, or other processes.
- Recycle oil, which does not need treatment before recycling, from cutting/machining operations.
- Collect recycle blast material from abrasive blasting operations.
- Using an on-site distillation unit reduces emissions, the cost of solvent disposal, and the cost of fresh solvent purchase.
- One shop recycled oil from cutting and machining operations where possible. Capital Cost: $1,900,000. Annual Savings: $156,000 (EPA).
- One company used 100,000 tons of blasting media in 2002. After adding total enclosures, the company used only 4,500 pounds of blasting media during the first half of 2003 (EPA).
- Blast cabinets, which enclose the blasting zone, are available in a variety of sizes and range from a few hundred dollars for a bench-top enclosure to several thousand dollars for large, multi-user systems (EPA).
- Capital costs for any new equipment necessary.
- Capital costs for batch skills can range from $2,600 to $17,000 (EPA).
- Training employees to use new procedures.
- See pages 69-70 of EPA's Sector Notebook Project: Fabricated Metal Products (PDF) (156 pp, 1.6 MB) for more case studies.
Change Processes
How?- Install an induction furnace for metal casting, which emits about 75% less particle pollution (dust) and fumes than other furnace types. An induction furnace does not require combustion gases or excessive metal temperatures.
- Centralize degreasing procedures to reduce and better track use of solvents.
- Remove all paint and solvents from the area to be welded to avoid generating toxic fumes during welding.
- Reduce the amount of fumes by using welding rods that produce a low fume, and by using the least amount of heat and toxic welding material allowed by the manufacturer's manuals.
- Switch to pulse welding, which lowers the welding fume generation rate, reduces spatter, and uses less energy.
- Reduces air emissions and dust generation.
- Reduces cost for solvent purchase.
- One shop precleaned using aluminum shot, which extended the life of aqueous or vapor degreasing solvent. Annual savings: $40,000. Payback period: 2 years. Waste reduction: 48,000 gallons of aqueous waste (EPA).
- Capital costs for any new equipment necessary.
- Training employees to use new procedures.
- See page 68 of EPA's Sector Notebook Project: Fabricated Metal Products (PDF) (156 pp, 1.6 MB) for more case studies.
Upgrade Equipment
How?- Check with state, local, and Tribal pollution prevention offices for funding possibilities.
- Pulse welding reduces welding fumes by 60 to 90%, welding spatter by 90%, and requires 10% less energy (EPA).
- Reduces air emissions.
- Reduces costs for raw materials and hazardous waste disposal.
- Capital costs for new equipment.
- Pulse welding requires equipment that is 2 to 3 times more expensive than constant voltage welding equipment. Machine life is also shorter, and the machines may be incompatible with older robotic adaptive controls (EPA).
- Training employees to use new equipment.