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United States Regulations
40 CFR PART 438—METAL PRODUCTS AND MACHINERY POINT SOURCE CATEGORY
PART 438—METAL PRODUCTS AND MACHINERY POINT SOURCE CATEGORY
Authority: 33 U.S.C. 1311, 1314, 1316, 1317, 1318, 1342 and 1361.
Source: 68 FR 25735, May 13, 2003, unless otherwise noted.
§ 438.1 General applicability.
(a) As defined more specifically in subpart A, except as provided in paragraphs (b) through (e) of this section, this part applies to process wastewater discharges from oily operations (as defined at §438.2(f) and appendix B of this part) to surface waters from existing or new industrial facilities (including facilities owned and operated by Federal, State, or local governments) engaged in manufacturing, rebuilding, or maintenance of metal parts, products, or machines for use in the Metal Product & Machinery (MP&M) industrial sectors listed in this section. The MP&M industrial sectors consist of the following:
Bus and Truck;
Miscellaneous Metal Products;
Mobile Industrial Equipment;
Precious Metals and Jewelry;
Ships and Boats; or
Stationary Industrial Equipment.
(b) The regulations in this part do not apply to process wastewaters from metal-bearing operations (as defined at §438.2(d) and appendix C of this part) or process wastewaters which are subject to the limitations and standards of other effluent limitations guidelines (e.g., Metal Finishing (40 CFR part 433) or Iron and Steel Manufacturing (40 CFR part 420)). The regulations in this part also do not apply to process wastewaters from oily operations (as defined at §438.2(f) and appendix B of this part) commingled with process wastewaters already covered by other effluent limitations guidelines or with process wastewaters from metal-bearing operations. This provision must be examined for each point source discharge at a given facility.
(c) Wastewater discharges resulting from the washing of cars, aircraft or other vehicles, when performed only for aesthetic or cosmetic purposes, are not subject to this part. Direct discharges resulting from the washing of cars, aircraft or other vehicles, when performed as a preparatory step prior to one or more successive manufacturing, rebuilding, or maintenance operations, are subject to this part.
(d) Wastewater discharges from railroad line maintenance facilities (as defined at §438.2(h)) are not subject to this part. Wastewater discharges from railroad overhaul or heavy maintenance facilities (as defined at §438.2(i)) may be covered by subpart A of this part, the Metal Finishing Point Source Category (40 CFR part 433), or by other effluent limitations guidelines, as applicable.
(e) The following wastewater discharges are not subject to this part:
(1) Non-process wastewater as defined at §438.2(e).
(2) Wastewater discharges introduced into a Publicly Owned Treatment Works (POTW) or a Federally owned and operated Treatment Works Treating Domestic Sewage (TWTDS), as defined at 40 CFR 122.2.
(3) Process wastewater generated by maintenance and repair activities at gasoline service stations, passenger car rental facilities, or utility trailer and recreational vehicle rental facilities.
(4) Wastewater discharges generated from gravure cylinder preparation or metallic platemaking conducted within or for printing and publishing facilities.
(5) Wastewater discharges in or on dry docks and similar structures, such as graving docks, building ways, marine railways, lift barges at shipbuilding facilities (or shipyards), and ships that are afloat.
(6) Wastewater generated by facilities primarily performing drum reconditioning and cleaning to prepare metal drums for resale, reuse, or disposal.
§ 438.2 General definitions.
As used in this part:
(a) The general definitions and abbreviations at 40 CFR part 401 shall apply.
(b) The regulated parameters are listed with approved methods of analysis in Table 1B at 40 CFR 136.3, and are defined as follows:
(1) O&G (as HEM) means total recoverable oil and grease measured as n-hexane extractable material.
(2) TSS means total suspended solids.
(c) Corrosion preventive coating means the application of removable oily or organic solutions to protect metal surfaces against corrosive environments. Corrosion preventive coatings include, but are not limited to: petrolatum compounds, oils, hard dry-film compounds, solvent-cutback petroleum-based compounds, emulsions, water-displacing polar compounds, and fingerprint removers and neutralizers. Corrosion preventive coating does not include electroplating, or chemical conversion coating operations.
(d) Metal-bearing operations means one or more of the following: abrasive jet machining; acid pickling neutralization; acid treatment with chromium; acid treatment without chromium; alcohol cleaning; alkaline cleaning neutralization; alkaline treatment with cyanide; anodizing with chromium; anodizing without chromium; carbon black deposition; catalyst acid pre-dip; chemical conversion coating without chromium; chemical milling (or chemical machining); chromate conversion coating (or chromating); chromium drag-out destruction; cyanide drag-out destruction; cyaniding rinse; electrochemical machining; electroless catalyst solution; electroless plating; electrolytic cleaning; electroplating with chromium; electroplating with cyanide; electroplating without chromium or cyanide; electropolishing; galvanizing/hot dip coating; hot dip coating; kerfing; laminating; mechanical and vapor plating; metallic fiber cloth manufacturing; metal spraying (including water curtain); painting-immersion (including electrophoretic, “E-coat”); photo imaging; photo image developing; photoresist application; photoresist strip; phosphor deposition; physical vapor deposition; plasma arc machining; plastic wire extrusion; salt bath descaling; shot tower—lead shot manufacturing; soldering; solder flux cleaning; solder fusing; solder masking; sputtering; stripping (paint); stripping (metallic coating); thermal infusion; ultrasonic machining; vacuum impregnation; vacuum plating; water shedder; wet air pollution control; wire galvanizing flux; and numerous sub-operations within those listed in this paragraph. In addition, process wastewater also results from associated rinses that remove materials that the preceding processes deposit on the surface of the workpiece. These metal-bearing operations are defined in appendix C of this part.
(e) Non-process wastewater means sanitary wastewater, non-contact cooling water, water from laundering, and non-contact storm water. Non-process wastewater for this part also includes wastewater discharges from non-industrial sources such as residential housing, schools, churches, recreational parks, shopping centers as well as wastewater discharges from gas stations, utility plants, and hospitals.
(f) Oily operations means one or more of the following: abrasive blasting; adhesive bonding; alkaline cleaning for oil removal; alkaline treatment without cyanide; aqueous degreasing; assembly/disassembly; burnishing; calibration; corrosion preventive coating (as defined in paragraph (c) of this section); electrical discharge machining; floor cleaning (in process area); grinding; heat treating; impact deformation; iron phosphate conversion coating; machining; painting-spray or brush (including water curtains); polishing; pressure deformation; solvent degreasing; steam cleaning; testing (e.g., hydrostatic, dye penetrant, ultrasonic, magnetic flux); thermal cutting; tumbling/barrel finishing/mass finishing/vibratory finishing; washing (finished products); welding; wet air pollution control for organic constituents; and numerous sub-operations within those listed in this paragraph. In addition, process wastewater also results from associated rinses that remove materials that the preceding processes deposit on the surface of the workpiece. These oily operations are defined in appendix B of this part.
(g) Process wastewater means wastewater as defined at 40 CFR parts 122 and 401, and includes wastewater from air pollution control devices.
(h) Railroad line maintenance facilities means facilities specified at §438.1 that only perform routine cleaning and light maintenance on railroad engines, cars, car-wheel trucks, or similar parts or machines, and discharge wastewater exclusively from oily operations (as defined in paragraph (f) of this section and appendix B of this part). These facilities only perform one or more of the following operations: assembly/disassembly, floor cleaning, maintenance machining (wheel truing), touch-up painting, and washing.
(i) Railroad overhaul or heavy maintenance facilities means facilities engaged in the manufacture, overhaul, or heavy maintenance of railroad engines, cars, car-wheel trucks, or similar parts or machines. These facilities typically perform one or more of the operations in paragraph (h) of this section and one or more of the following operations: abrasive blasting, alkaline cleaning, aqueous degreasing, corrosion preventive coating, electrical discharge machining, grinding, heat treating, impact deformation, painting, plasma arc machining, polishing, pressure deformation, soldering/brazing, stripping (paint), testing, thermal cutting, and welding.
Subpart A—Oily Wastes
§ 438.10 Applicability.
(a) This subpart applies to process wastewater directly discharged from facilities specified at §438.1.
(b) This subpart applies to process wastewater discharges from oily operations (as defined at §438.2(f) and appendix B of this part).
(c) This subpart does not apply to process wastewater discharges from metal-bearing operations (as defined at §438.2(d) and appendix C of this part).
§ 438.12 Effluent limitations attainable by the application of the best practicable control technology currently available (BPT).
Except as provided at 40 CFR 125.30 through 125.32, any existing point source subject to this subpart must achieve the following effluent limitations representing the application of BPT. Discharges must remain within the pH range 6 to 9 and must not exceed the following:
Regulated parameter daily \1\
1. TSS....................................................... 62
2. O&G (as HEM).......................................... 46
\1\ mg/L (ppm).
§ 438.13 Effluent limitations attainable by application of the best control technology for conventional pollutants (BCT).
Except as provided at 40 CFR 125.30 through 125.32, any existing point source subject to this subpart must achieve the following effluent limitation representing the application of BCT: Limitations for TSS, O&G (as HEM) and pH are the same as the corresponding limitation specified at §438.12.
§ 438.15 New source performance standards (NSPS).
New point sources subject to this subpart must achieve the new source performance standards (NSPS) for TSS, O&G (as HEM), and pH, which are the same as the corresponding limitation specified at §438.12. The performance standards apply with respect to each new point source that commences discharge after June 12, 2003.
Appendix A to Part 438—Typical Products in Metal Products and Machinery Sectors
AEROSPACE AIRCRAFT BUS & TRUCK
Guided Missiles & Aircraft Engines & Bus Terminal &
Space Vehicle Engine Parts Service Facilities
Guided Missile & Aircraft Frames Courier Services,
Space Vehicle Prop Manufacturing Except by Air Freight
Other Space Vehicle Aircraft Parts & Truck Terminals, W/
& Missile Parts Equipment or W/O Maintenance.
Airports, Flying Intercity & Rural
Fields, & Services Highways (Buslines)
Local & Suburban
Transit (Bus &
Trans. (Lim., Amb.,
Local Trucking With
Local Trucking Without
Motor Vehicle Parts
Truck & Bus Bodies
ELECTRONIC EQUIPMENT HARDWARE HOUSEHOLD EQUIPMENT
Communications Architectural & Commercial, Ind. &
Equipment Ornamental Metal Work Inst. Elec. Lighting
Connectors for Bolts, Nuts, Screws, Fixtures
Electronic Rivets & Washers Current-Carrying
Applications Crowns & Closures Wiring Devices
Electric Lamps Cutlery Electirc Housewares
Electron Tubes Fabricated Metal & Fans
Electronic Capacitors Products Electric Lamps
Electronic Coils & Fabricated Pipe & Farm Freezers
Transformers Fabricated Pipe Household Appliances
Electronic Components Fittings Household Cooking
Radio & TV Fabricated Plate Work Equipment
Communications (Boiler Shops) Household Refrig.
Equipment Fabricated Structural & Home & Farm
Telephone & Metal Freezers
Telegraph Apparatus Fasteners, Buttons, Household Laundry
Needles & Pins Equipment
Fluid Power Values Household Vacuum
& Hose Fittings Cleaners
Hand & Edge Tools Lighting Equipment
Hand Saws & Saw Noncurrent-Carrying
Blades Wiring Devices
Hardware Radio & Television
Heating Equipment, Repair Shops
Except Electric Radio & Television
Industrial Furnaces Sets Except Commn.
& Ovens Types
Iron & Steel Refrig. & Air
Forgings Cond. Serv. &
Machine Tool Repair Shops
Accessories & Residential Electrical
Measuring Devices Lighting Fixtures
Machine Tools, Metal
Machine Tools, Metal
Metal Shipping Barrels,
Drums, Kegs, Pails
Power Driven Hand Tools
Screw Machine Products
Sheet Metal Work
Special Dies &
Tools, Die Sets, Jigs,
Valves & Pipe
INSTRUMENTS MOBILE INDUSTRIAL MOTOR VEHICLE
Analytical Instruments EQUIPMENT Auto Exhaust System
Automatic Environmental Construction Machinery Repair Shops
Controls & Equipment Automobile Dealers
Coating, Engraving, Farm Machinery & (new & used)
& Allied Services Equipment Auto. Dealers
Dental Equipment & Garden Tractors & (Dunebuggy, Go-cart,
Supplies Lawn & Garden Snowmobile)
Ophthalmic Goods Equipment Automobile Service
Fluid Meters & Hoist, Industrial (includes Diag. &
Counting Devices Cranes & Monorails Insp. Cntrs.)
Instruments to Measure Industrial Trucks, Automotive Equipment
Electricity Tractors, Trailers, Automotive Glass
Laboratory Apparatus Tanks & Tank Replacement Shops
& Furniture Components Automotive Repairs
Manufacturing Mining machinery & Shops
Industries equipment, except oil Automotive Stampings
Measuring & field Automotive
Controlling Devices Transmission Repair
Optical Instruments Shops
& Lenses Carburetors, Pistons
Orthopedic, Prosthetic, Rings, Values
& Surgical Electrical Equipment
Supplies for Motor
Pens, Mechanical General Automotive
Pencils, & Parts Repair Shops
Process Control Mobile Homes
Instruments Motor Vehicle &
Search & Navigation Automotive Bodies
Equipment Motor Vehicle Parts
Surgical & Medical & Accessories
Instruments & Motorcycle Dealers
Watches, Clocks, Passenger Car Leasing
Associated Devices Recreational &
& Parts Utility Trailer
Top & Body Repair
& Paint Shops
Travel Trailers &
INSTRUMENTS OFFICE ORDNANCE PRECIOUS METALS &
MACHINE Ammunition JEWELRY
Calculating & Ordnance & Costume Jewelry
Accounting Equipment Accessories Jewelers' Materials
Computer Maintenance Small Arms & Lapidary Work
& Repair Small Arms Ammunition Jewelry, Precious
Computer Peripheral Metal
Equipment Musical Instruments
Computer Related Silverware, Plated
Services Ware, & Stainless
Computer Rental &
RAILROAD SHIPS & BOATS STATIONARY INDUSTRIAL
Line-Haul Railroads Boat Building & EQUIPMENT
Railcars, Railway Repairing Air & Gas
Systems Deep Sea Domestic Compressors
Switching & Transportation of Automatic Vending
Terminal Stations Freight Machines
Deep Sea Passenger Ball & Roller
Transportation, Except Bearings
by Ferry Blowers & Exhaust
Freight Transportation & Ventilation
on the Great Lakes Fans
Marinas Commercial Laundry
Ship Building & Equipment
Repairing Conveyors &
Towing & Tugboat Conveying Equipment
Service Electric Industrial
Water Passenger Apparatus
Transportation Ferries Elevators & Moving
Water Transportation of Stairways
Freight Equipment Rental &
Water Transportation Leasing
Services Food Product Machinery
Fluid Power Cylinders
Fluid Power Pumps
Furnaces & Ovens
Oil Field Machinery
Pumps & Pumping
Air & Heating
Rolling Mill Machinery
Scales & Balances,
Speed Changers, High
Speed Drivers &
Steam, Gas, Hydraulic
Shops & Related
Appendix B to Part 438—Oily Operations Definitions
Note: The definitions in this appendix shall not be used to differentiate between the six “core” metal finishing operations (i.e., Electroplating, Electroless Plating, Anodizing, Coating (chromating, phosphating, and coloring), Chemical Etching and Milling, and Printed Circuit Board Manufacture) and forty “ancillary” process operations listed at 40 CFR 433.10(a).
Abrasive Blasting involves removing surface film from a part by using abrasive directed at high velocity against the part. Abrasive blasting includes bead, grit, shot, and sand blasting, and may be performed either dry or with water. The primary applications of wet abrasive blasting include: Removing burrs on precision parts; producing satin or matte finishes; removing fine tool marks; and removing light mill scale, surface oxide, or welding scale. Wet blasting can be used to finish fragile items such as electronic components. Also, some aluminum parts are wet blasted to achieve a fine-grained matte finish for decorative purposes. In abrasive blasting, the water and abrasive typically are reused until the particle size diminishes due to impacting and fracture.
Adhesive Bonding involves joining parts using an adhesive material. Typically, an organic bonding compound is used as the adhesive. This operation usually is dry; however, aqueous solutions may be used as bonding agents or to contain residual organic bonding materials.
Alkaline Cleaning for Oil Removal is a general term for the application of an alkaline cleaning agent to a metal part to remove oil and grease during the manufacture, maintenance, or rebuilding of a metal product. This unit operation does not include washing of the finished products after routine use (as defined in “Washing (Finished Products)” in this appendix), or applying an alkaline cleaning agent to remove nonoily contaminants such as dirt and scale (as defined in “Alkaline Treatment Without Cyanide” in this appendix and “Alkaline Treatment With Cyanide” in appendix C of this part). Wastewater generated includes spent cleaning solutions and rinse waters.
(1) Alkaline cleaning is performed to remove foreign contaminants from parts. This operation usually is done prior to finishing (e.g., electroplating).
(2) Emulsion cleaning is an alkaline cleaning operation that uses either complex chemical enzymes or common organic solvents (e.g., kerosene, mineral oil, glycols, and benzene) dispersed in water with the aid of an emulsifying agent. The pH of the solvent usually is between 7 and 9, and, depending on the solvent used, cleaning is performed at temperatures from room temperature to 82 °C (180 °F). This operation often is used as a replacement for vapor degreasing.
Alkaline Treatment Without Cyanide is a general term used to describe the application of an alkaline solution not containing cyanide to a metal surface to clean the metal surface or prepare the metal surface for further surface finishing.
Aqueous Degreasing involves cleaning metal parts using aqueous-based cleaning chemicals primarily to remove residual oils and greases from the part. Residual oils can be from previous operations (e.g., machine coolants), oil from product use in a dirty environment, or oil coatings used to inhibit corrosion. Wastewater generated by this operation includes spent cleaning solutions and rinse waters.
Assembly/Disassembly involves fitting together previously manufactured or rebuilt parts or components into a complete metal product or machine or taking a complete metal product or machine apart. Assembly/disassembly operations are typically dry; however, special circumstances can require water for cooling or buoyancy. Also, rinsing may be necessary under some conditions.
Burnishing involves finish sizing or smooth finishing a part (previously machined or ground) by displacing, rather than removing, minute surface irregularities with smooth point or line-contact, fixed or rotating tools. Lubricants or soap solutions can be used to cool the tools used in burnishing operations. Wastewater generated during burnishing include process solutions and rinse water.
Calibration is performed to provide reference points for the use of a product. This unit operation typically is dry, although water may be used in some cases (e.g., pumping water for calibration of a pump). Water used in this unit operation usually does not contain additives.
Corrosion Preventive Coating involves applying removable oily or organic solutions to protect metal surfaces against corrosive environments. Corrosion preventive coatings include, but are not limited to: Petrolatum compounds, oils, hard dry-film compounds, solvent-cutback petroleum-based compounds, emulsions, water-displacing polar compounds, and fingerprint removers and neutralizers. Corrosion preventive coating does not include electroplating, or chemical conversion coating operations. Many corrosion preventive materials also are formulated to function as lubricants or as a base for paint. Typical applications include: Assembled machinery or equipment in standby storage; finished parts in stock or spare parts for replacement; tools such as drills, taps, dies, and gauges; and mill products such as sheet, strip, rod and bar. Wastewater generated during corrosion preventive coating includes spent process solutions and rinses. Process solutions are discharged when they become contaminated with impurities or are depleted of constituents. Corrosion preventive coatings typically do not require an associated rinse, but parts are sometimes rinsed to remove the coating before further processing.
Electrical Discharge Machining involves removing metals by a rapid spark discharge between different polarity electrodes, one the part and the other the tool, separated by a small gap. The gap may be filled with air or a dielectric fluid. This operation is used primarily to cut tool alloys, hard nonferrous alloys, and other hard-to-machine materials. Most electrical discharge machining processes are operated dry; however, in some cases, the process uses water and generates wastewater containing dielectric fluid.
Floor Cleaning (in Process Area) removes dirt, debris, and process solution spills from process area floors. Floors can be cleaned using wet or dry methods, such as vacuuming, mopping, dry sweeping, and hose rinsing. Non-process area floor cleaning in offices and other similar non-process areas is not included in this unit operation.
Grinding involves removing stock from a part by using abrasive grains held by a rigid or semirigid binder. Grinding shapes or deburrs the part. The grinding tool usually is a disk (the basic shape of grinding wheels), but can also be a cylinder, ring, cup, stick, strip, or belt. The most commonly used abrasives are aluminum oxide, silicon carbide, and diamond. The process may use a grinding fluid to cool the part and remove debris or metal fines. Wastewater generated during grinding includes spent coolants and rinses. Metal-working fluids become spent for a number of reasons, including increased biological activity (i.e., the fluids become rancid) or decomposition of the coolant additives. Rinse waters typically are assimilated into the working fluid or treated on site.
Heat Treating involves modifying the physical properties of a part by applying controlled heating and cooling cycles. This operation includes tempering, carburizing, cyaniding, nitriding, annealing, aging, normalizing, austenitizing, austempering, siliconizing, martempering, and malleablizing. Parts are heated in furnaces or molten salt baths, and then may be cooled by quenching in aqueous solutions (e.g., brine solutions), neat oils (pure oils with little or no impurities), or oil/water emulsions. Heat treating typically is a dry operation, but is considered a wet operation if aqueous quenching solutions are used. Wastewater includes spent quench water and rinse water.
Impact Deformation involves applying impact force to a part to permanently deform or shape it. Impact deformation may include mechanical processes such as hammer forging, shot peening, peening, coining, high-energy-rate forming, heading, or stamping. Natural and synthetic oils, light greases, and pigmented lubricants are used in impact deformation operations. Pigmented lubricants include whiting, lithapone, mica, zinc oxide, molybdenum disulfide, bentonite, flour, graphite, white lead, and soap-like materials. These operations typically are dry, but wastewater can be generated from lubricant discharge and from rinsing operations associated with the operation.
Iron Phosphate Conversion Coating is the process of applying a protective coating on the surface of a metal using a bath consisting of a phosphoric acid solution containing no metals (e.g., manganese, nickel, or zinc) or a phosphate salt solution (i.e., sodium or potassium salts of phosphoric acid solutions) containing no metals (e.g., manganese, nickel, or zinc) other than sodium or potassium. Any metal concentrations in the bath are from the substrate.
Machining involves removing stock from a part (as chips) by forcing a cutting tool against the part. This includes machining processes such as turning, milling, drilling, boring, tapping, planing, broaching, sawing, shaving, shearing, threading, reaming, shaping, slotting, hobbing, and chamfering. Machining processes use various types of metal-working fluids, the choice of which depends on the type of machining being performed and the preference of the machine shop. The fluids can be categorized into four groups: Straight oil (neat oils), synthetic, semisynthetic, and water-soluble oil. Machining operations generate wastewater from working fluid or rinse water discharge. Metal-working fluids periodically are discarded because of reduced performance or development of a rancid odor. After machining, parts are sometimes rinsed to remove coolant and metal chips. The coolant reservoir is sometimes rinsed, and the rinse water is added to the working fluid.
Painting-Spray or Brush (Including Water Curtains) involves applying an organic coating to a part. Coatings such as paint, varnish, lacquer, shellac, and plastics are applied by spraying, brushing, roll coating, lithographing, powder coating, and wiping. Water is used in painting operations as a solvent (water-borne formulations) for rinsing, for cleanup, and for water-wash (or curtain) type spray booths. Paint spray booths typically use most of the water in this unit operation. Spray booths capture overspray (i.e., paint that misses the product during application), and control the introduction of pollutants into the workplace and environment.
Polishing involves removing stock from a part using loose or loosely held abrasive grains carried to the part by a flexible support. Usually, the objective is to achieve a desired surface finish or appearance rather then to remove a specified amount of stock. Buffing is included in this unit operation, and usually is performed using a revolving cloth or sisal buffing wheel, which is coated with a suitable compound. Liquid buffing compounds are used extensively for large-volume production on semiautomated or automated buffing equipment. Polishing operations typically are dry, although liquid compounds and associated rinses are used in some polishing processes.
Pressure Deformation involves applying force (other than impact force) to permanently deform or shape a part. Pressure deformation may include rolling, drawing, bending, embossing, sizing, extruding, squeezing, spinning, necking, forming, crimping or flaring. These operations use natural and synthetic oils, light greases, and pigmented lubricants. Pigmented lubricants include whiting, lithapone, mica, zinc oxide, molybdenum disulfide, bentonite, flour, graphite, white lead, and soap-like materials. Pressure deformation typically is dry, but wastewater is sometimes generated from the discharge of lubricants or from rinsing associated with the process.
Solvent Degreasing removes oils and grease from the surface of a part using organic solvents, including aliphatic petroleum (e.g., kerosene, naphtha), aromatics (e.g., benzene, toluene), oxygenated hydrocarbons (e.g., ketones, alcohol, ether), and halogenated hydrocarbons (e.g., 1,1,1-trichloroethane, trichloroethylene, methylene chloride). Solvent cleaning takes place in either the liquid or vapor phase. Solvent vapor degreasing normally is quicker than solvent liquid degreasing. However, ultrasonic vibration is sometimes used with liquid solvents to decrease the required immersion time of complex shapes. Solvent cleaning often is used as a precleaning operation prior to alkaline cleaning, as a final cleaning of precision parts, or as surface preparation for some painting operations. Solvent degreasing operations typically are not followed by rinsing, although rinsing is performed in some cases.
Steam Cleaning removes residual dirt, oil, and grease from parts after processing though other unit operations. Typically, additives are not used in this operation; the hot steam removes the pollutants. Wastewater is generated when the cleaned parts are rinsed.
Testing (e.g., hydrostatic, dye penetrant, ultrasonic, magnetic flux) involves applying thermal, electrical, mechanical, hydraulic, or other energy to determine the suitability or functionality of a part, assembly, or complete unit. Testing also may include applying surface penetrant dyes to detect surface imperfections. Other examples of tests frequently performed include electrical testing, performance testing, and ultrasonic testing; these tests typically are dry but may generate wastewater under certain circumstances. Testing usually is performed to replicate some aspect of the working environment. Wastewater generated during testing includes spent process solutions and rinses.
Thermal Cutting involves cutting, slotting, or piercing a part using an oxy-acetylene oxygen lance, electric arc cutting tool, or laser. Thermal cutting typically is a dry process, except for the use of contact cooling waters and rinses.
Tumbling/Barrel Finishing/Mass Finishing/Vibratory Finishing involves polishing or deburring a part using a rotating or vibrating container and abrasive media or other polishing materials to achieve a desired surface appearance. Parts to be finished are placed in a rotating barrel or vibrating unit with an abrasive media (e.g., ceramic chips, pebbles), water, and chemical additives (e.g., alkaline detergents). As the barrel rotates, the upper layer of the part slides toward the lower side of the barrel, causing the abrading or polishing. Similar results can be achieved in a vibrating unit, where the entire contents of the container are in constant motion, or in a centrifugal unit, which compacts the load of media and parts as the unit spins and generates up to 50 times the force of gravity. Spindle finishing is a similar process, where parts to be finished are mounted on fixtures and exposed to a rapidly moving abrasive slurry. Wastewater generated during barrel finishing includes spent process solutions and rinses. Following the finishing process, the contents of the barrel are unloaded. Process wastewater is either discharged continuously during the process, discharged after finishing, or collected and reused. The parts are sometimes given a final rinse to remove particles of abrasive media.
Washing (Finished Products) involves cleaning finished metal products after use or storage using fresh water or water containing a mild cleaning solution. This unit operation applies only to the finished products that do not require maintenance or rebuilding.
Welding involves joining two or more pieces of material by applying heat, pressure, or both, with or without filler material, to produce a metallurgical bond through fusion or recrystallization across the interface. This includes gas welding, resistance welding, arc welding, cold welding, electron beam welding, and laser beam welding. Welding typically is a dry process, except for the occasional use of contact cooling waters or rinses.
Wet Air Pollution Control for Organic Constituents involves using water to remove organic constituents that are entrained in air streams exhausted from process tanks or production areas. Most frequently, wet air pollution control devices are used with cleaning and coating processes. A common type of wet air pollution control is the wet packed scrubber consisting of a spray chamber that is filled with packing material. Water is continuously sprayed onto the packing and the air stream is pulled through the packing by a fan. Pollutants in the air stream are absorbed by the water droplets and the air is released to the atmosphere. A single scrubber often serves numerous process tanks.
Appendix C to Part 438—Metal-Bearing Operations Definitions
Note: The definitions in this appendix shall not be used to differentiate between the six “core” metal finishing operations (i.e., Electroplating, Electroless Plating, Anodizing, Coating (chromating, phosphating, and coloring), Chemical Etching and Milling, and Printed Circuit Board Manufacture) and forty “ancillary” process operations listed at 40 CFR 433.10(a).
Abrasive Jet Machining includes removing stock material from a part by a high-speed stream of abrasive particles carried by a liquid or gas from a nozzle. Abrasive jet machining is used for deburring, drilling, and cutting thin sections of metal or composite material. Unlike abrasive blasting, this process operates at pressures of thousands of pounds per square inch. The liquid streams typically are alkaline or emulsified oil solutions, although water also can be used.
Acid Pickling Neutralization involves using a dilute alkaline solution to raise the pH of acid pickling rinse water that remains on the part after pickling. The wastewater from this operation is the acid pickling neutralization rinse water.
Acid Treatment With Chromium is a general term used to describe any application of an acid solution containing chromium to a metal surface. Acid cleaning, chemical etching, and pickling are types of acid treatment. Chromic acid is used occasionally to clean cast iron, stainless steel, cadmium and aluminum, and bright dipping of copper and copper alloys. Also, chromic acid solutions can be used for the final step in acid cleaning phosphate conversion coating systems. Chemical conversion coatings formulated with chromic acid are defined at “Chromate Conversion Coating (or Chromating)” in this appendix. Wastewater generated during acid treatment includes spent solutions and rinse waters. Spent solutions typically are batch discharged and treated or disposed of off site. Most acid treatment operations are followed by a water rinse to remove residual acid.
Acid Treatment Without Chromium is a general term used to describe any application of an acid solution not containing chromium to a metal surface. Acid cleaning, chemical etching, and pickling are types of acid treatment. Wastewater generated during acid treatment includes spent solutions and rinse waters. Spent solutions typically are batch discharged and treated or disposed of off site. Most acid treatment operations are followed by a water rinse to remove residual acid.
Alcohol Cleaning involves removing dirt and residue material from a part using alcohol.
Alkaline Cleaning Neutralization involves using a dilute acid solution to lower the pH of alkaline cleaning rinse water that remains on the part after alkaline cleaning. Wastewater from this operation is the alkaline cleaning neutralization rinse water.
Alkaline Treatment With Cyanide is the cleaning of a metal surface with an alkaline solution containing cyanide. Wastewater generated during alkaline treatment includes spent solutions and rinse waters. Alkaline treatment solutions become contaminated from the introduction of soils and dissolution of the base metal. They usually are treated and disposed of on a batch basis. Alkaline treatment typically is followed by a water rinse that is discharged to a treatment system.
Anodizing With Chromium involves producing a protective oxide film on aluminum, magnesium, or other light metal, usually by passing an electric current through an electrolyte bath in which the metal is immersed. Anodizing may be followed by a sealant operation. Chromic acid anodic coatings have a relatively thick boundary layer and are more protective than are sulfuric acid coatings. For these reasons, chromic acid is sometimes used when the part cannot be rinsed completely. These oxide coatings provide corrosion protection, decorative surfaces, a base for painting and other coating processes, and special electrical and mechanical properties. Wastewaters generated during anodizing include spent anodizing solutions, sealants, and rinse waters. Because of the anodic nature of the process, anodizing solutions become contaminated with the base metal being processed. These solutions eventually reach an intolerable concentration of dissolved metal and require treatment or disposal. Rinse water following anodizing, coloring, and sealing typically is discharged to a treatment system.
Anodizing Without Chromium involves applying a protective oxide film to aluminum, magnesium, or other light metal, usually by passing an electric current through an electrolyte bath in which the metal is immersed. Phosphoric acid, sulfuric acid, and boric acid are used in anodizing. Anodizing also may include sealant baths. These oxide coatings provide corrosion protection, decorative surfaces, a base for painting and other coating processes, and special electrical and mechanical properties. Wastewater generated during anodizing includes spent anodizing solutions, sealants, and rinse waters. Because of the anodic nature of the process, anodizing solutions become contaminated with the base metal being processed. These solutions eventually reach an intolerable concentration of dissolved metal and require treatment or disposal. Rinse water following anodizing, coloring, and sealing steps typically is discharged to a treatment systems.
Carbon Black Deposition involves coating the inside of printed circuit board holes by dipping the circuit board into a tank that contains carbon black and potassium hydroxide. After excess solution dips from the circuit boards, they are heated to allow the carbon black to adhere to the board.
Catalyst Acid Pre-Dip uses rinse water to remove residual solution from a part after the part is processed in an acid bath. The wastewater generated in this unit operation is the rinse water.
Chemical Conversion Coating without Chromium is the process of applying a protective coating on the surface of a metal without using chromium. Such coatings are applied through phosphate conversion (except for “Iron Phosphate Conversion Coating,” see appendix B of this part), metal coloring, or passivation. Coatings are applied to a base metal or previously deposited metal to increase corrosion protection and lubricity, prepare the surface for additional coatings, or formulate a special surface appearance. This unit process includes sealant operations that use additives other than chromium.
(1) In phosphate conversion, coatings are applied for one or more of the following reasons: to provide a base for paints and other organic coatings; to condition surfaces for cold forming operations by providing a base for drawing compounds and lubricants; to impart corrosion resistance to the metal surface; or to provide a suitable base for corrosion-resistant oils or waxes. Phosphate conversion coatings are formed by immersing a metal part in a dilute solution of phosphoric acid, phosphate salts, and other reagents.
(2) Metal coloring by chemical conversion coating produces a large group of decorative finishes. Metal coloring includes the formation of oxide conversion coatings. In this operation, the metal surface is converted into an oxide or similar metallic compound, giving the part the desired color. The most common colored finishes are used on copper, steel, zinc, and cadmium. (continued)