40 CFR 63, Subpart 6W
Section 112(c)(3) (US Code 7412) of the Clean Air Act required EPA to list sufficient categories or subcategories of area sources [PDF] to ensure that area sources representing 90 percent of the emissions of the 30 urban HAP (hazardous air pollutants) are subject to regulation. One of the categories was identified as ‘Polishing and Plating.’
On June 12, 2008, EPA issued final air toxics standards for the plating and polishing area source category. This final rule established emission standards in the form of management practices for new and existing tanks, thermal spraying equipment and mechanical polishing equipment in certain plating and polishing processes.
The application of a non-electrolytic coating, also known as a pretreatment, promotes stronger adhesive of subsequent coatings such as the application of paint bind. The pretreatment can also provide some corrosion protection. Pretreatments can include conversion coatings which can include oxide (black oxide and anodizing), phosphate and chromate coatings.
Pretreatments based on zirconium oxide are being used commercially in automotive and other industrial operations as replacements to hexavalent chromium-based and zinc phosphate pretreatments.
Sometimes what follows an oxide coating is a seal.
Sealing is a process of chemical change whereby oxide coating is converted into a more chemically stable hydrated form, which will better resist the attack of the atmosphere and chemicals. Most common is the use of hot water [solution]. Less common is the use of Nickel Acetate and Sodium Dichromate.
What does it affect?
This regulation affects emissions of Cadmium, Chromium, Lead, Manganese, and/or Nickel from any of the following operations:
Electrolytic metal coating processes
- Cadmium, lead, nickel, or lead electroplating
- Electroforming
- Electropolishing
Non-electrolytic metal coating processes
- Electroless nickel plating *
- Chromate conversion coating *
- Manganese phosphating *
- Nickel acetate sealing *
- Sodium dichromate sealing *
- Thermal metal spraying
- Dry mechanical polishing after plating
* Subject only to applicable management practices (12 listed in 40 CFR 63, Subpart WWWWWW), as practicable, as well as reporting and recordkeeping. It is likely that each of these practices have been evaluated as to their practicability.
What is exempt from this regulation?
This regulation exempts the following operations:
- Hard and decorative chromium electroplating
- Chromium anodizing
- Plating and polishing conducted for:
- Research and development
- Education
- Repair of surfaces or equipment
- Restoration of the original finish
- Dry mechanical polishing prior to plating
- Trace quantities of any one of the five (5) metals
Please note a business is exempt from this regulation if it has been determined to be a major source of hazardous air pollutants (HAP). If in doubt, contact CTAP. Please use the consultation request form.
Control and Management Practices
The following resources contain further information regarding control and management practices of specific operations.
- Electroplating (non-cyanide), Electroforming, or Electropolishing [PDF]
- Electroplating (utilizing cyanide) [PDF]
- Dry Mechanical Polishing [PDF]
- Flash or Short-Term Electroplating [PDF]
- Thermal Spraying [PDF]