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Pollution Prevention and Control Technologies for Plating Operations


Section 2 - General Waste Reduction Practices

2.3 GOOD OPERATING PRACTICES

2.3.3 Chemical Purchasing, Storage, Usage, and Handling

Proper purchasing, storage, usage, and handling of chemicals increases the percentage of raw materials that reach their intended process without spills, leaks or other types of losses that could result in waste generation. Some basic guidelines for good operating practices include (ref. 303):

  • Purchasing:
    • Standardization of materials, i.e., using the minimum number of materials in all operations. Many times the decision to use one material over another is based on operator preference, rather than on a technical or economic requirement. Written specifications can improve purchasing and reduce waste (PS 257).
    • Avoid over-purchase of materials.
    • Avoid collecting free samples of process chemicals from vendors. Only accept amounts needed for testing purposes.
  • Storage:
    • Utilize a dedicated/protected storage area.
    • Space containers in storage areas to facilitate inspection.
    • Label all containers.
    • Stack containers according to manufacturers' instructions to prevent cracking and tearing from improper weight distribution.
    • Separate incompatible materials in storage such as cyanides and acids.
    • Raise containers off the floor in the storage area to inhibit corrosion from ÒsweatingÓ concrete.
  • Handling/Use:
    • Establish written procedures for process (tank) formulation and additions.
    • Use specifically assigned personnel to formulate baths and make tank additions.
    • Perform routine bath analyses and maintain bath analyses logs and tank formulation/addition logs.
    • Use process baths to the maximum extent possible (do not employ a dump schedule).
    • Remove zinc anodes from the baths when they are idle to prevent a buildup of metal in the baths.
    • Implement multiple use of certain materials (e.g., soak cleaner is reused as an electrocleaner by PS 068).
    • Implement statistical process control (SPC) to improve the efficiency of chemical use (PS 257).

Survey questions that relate to chemical usage, handling and storage include questions 4, 5, 6, 7, 8, 9, and 10 (Exhibit 2-6). The responses to several of these questions were previously discussed in Section 2.3.3. The response to question 5 indicated that 273 shops (or 85.8%) use specifically assigned personnel for chemical additions and the response to question 8 indicated that 229 shops (or 72.0%) have written procedures for bath make-up and chemical additions. These two pollution prevention options received particularly high average success ratings. The response to question 9 indicates that 234 shops (or 73.6%) use process baths to the maximum extent possible rather than employ a dump schedule and the response to question 10 indicates that 78 shops (or 24.5% of all shops or approximately one-half of shops performing cadmium and/or zinc plating) remove cadmium or zinc anodes from baths when they are idle. The latter practice prevents a buildup of dissolved metal in the bath, particularly with zinc plating.


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