Powder coating is the most exciting finishing method to be introduced in the past one hundred years. Powder coating offers significant performance advantages, an excellent solution to meeting current environmental regulations, a good balance of mechanical properties, and excellent corrosion resistance.

Economic Advantages

Powder coating systems save energy and virtually eliminate air and water pollution because they are solvent-free. The need for air make-up and the high cost of heating is reduced, resulting in considerable energy savings. Costly anti-pollution equipment and time and money spent dealing with state and federal regulatory agencies is also reduced. There is a major reduction in expensive and difficult disposal problems because there is no liquid paint sludge to send to a hazardous waste site. Because powder coatings do not require any flash-off time, conveyor racks can be more closely spaced; more parts coated per hour means a lower unit cost. In addition to the increased production rate for a powder coating system, reject rates are much lower than in a wet system.

Environmental Advantages

The Clean Air Act of 1970 [U.S. Law] propelled powder coating processes to the forefront of the industry. By eliminating volatile organic compounds (VOCs), air pollution was reduced. To many major coating companies, The Clean Air Act signaled the end of solvent-based processes. Prior to that, the fluidized bed coating process was well established and though the electrostatic powder spray process had started to gain acceptance, powder coating processes in general were not widespread or commercially accepted. The powder coating method received more media attention between 1971 and 1975 than at any other time, before or after. Powder coating processes, especially electrostatic powder spray processes, are now universally accepted and specified as the Best Available Control Technology (BACT) to reduce air pollution. While powder coatings have many process and performance advantages over conventionally applied coatings, it is the ecological

advantages that advance their growth and acceptance. Consider:

Powder Coatings Contain No Solvents or VOCs

• No VOC emissions to the atmosphere.

• Compliance with most environmental regulations.

• Permits may not be required or are typically easier to obtain for new booth installations.

• Administrative costs of inspections, permits, sample testing, and record keeping are significantly reduced.

• Coating booth exhaust air is returned to the coating room.

• Less oven air is exhausted to the outside.

• Inherently safer and cleaner than solvent-based paint systems.

• No special transportation, storage, or handling techniques required.

Powder Coatings Reduce Waste and Present Few Hazards

• In most systems, powder coatings are collected and recycled.

• First pass transfer efficiency is high compared to conventional liquid paint application.

• Almost all powder coatings are free of heavy metals.

• The Resources Conservation and Recovery Act (RCRA) regulations consider almost no powder coating a hazardous waste.

• In most states, disposal methods for waste powder are the same as for non-hazardous industrial wastes.

Mechanical Properties

The general purpose powder coating formulations, now widely used, have a long established reputation for providing an excellent balance of mechanical properties including impact and abrasion resistance, and hardness. Resources now available allow for an even broader range of film properties than ever before. Extra hardness, greater chemical resistance, improved exterior gloss retention, and superior flexibility, though not necessarily in a single formulation, are all attainable. There are very few film properties available from liquid paint finishes that cannot be achieved with powder; however, some film properties easily attainable with powder are difficult or impossible to achieve with conventional wet paints.

ASTM Test Results

Dry powder paint sucessfully passed the following ASTM specified tests:

• Salt Spray Test (500 hours)

• Humidity Test (500 hours)

• QUV Test (500 hours)

• Test Fence (17 months) (test for gloss retention)

• Impact Test (140 inch pounds)

• Cold and High Temperature Test

• Adhesion Test

• Hardness Test

• Flexibility Test

• Chemical Resistance Tests:
  ­ Gasoline (unleaded, 24 hour immersion test)

  ­ Mineral Spirits (24 hour immersion test)

  ­ Nitric Acid (10% solution spot test for blistering)

  ­ Hydrochloric Acid (10% solution spot test for blistering)

  ­ Sulfuric Acid (10% solution spot test for blistering)

  ­ Sodium Hydroxide (10% solution spot test for blistering)

  ­ LP-Gas Soak Test

  ­ Anhydrous Ammonia Reactivity Test

  Figure 1.

  
  
  ANSI 49 Gray Powder Paint with Aluminum Oxide Coated Fasteners.

  Figure 2.

  
  
  Inside and Outside Surfaces Coated for Corrosion Protection Eliminating the need for Chromate Conversion.

  Figure 3.

  
  
  Standard Liquid Paint Coating after ASTM B117 500 Hour Salt Spray Test.

  Figure 4.

  
  
  Dry Powder Paint and Aluminum Oxide Coated Fasteners after ASTM B117 500 Hour Salt Spray Test.