Epoxy Powder Coating

Pure epoxy powder coating is not recommended for long-term outdoor applications due to its poor UV resistance. They will quickly pulverize, fade, and lose their luster in sunlight. For outdoor applications, epoxy polyester hybrid powder coatings (with improved weather resistance but still not suitable for harsh outdoor conditions), pure polyester powder coatings, or polyurethane powder coatings are usually chosen, which have better weather resistance and UV resistance. Sometimes, epoxy powder coating is used as a primer for outdoor products, and then covered with a more weather resistant topcoat.

The cured coating of ordinary epoxy powder coating can usually withstand temperatures of about 120 ° C (about 250 ° F). Some special formulations of epoxy powder coatings may have higher heat resistance. If higher temperature resistance is required, other types of powder coatings such as silicone based powder coatings may need to be considered.

Essentially, there isn’t much difference. The term ‘Fusion Bonded Epoxy’ (FBE) is commonly used in specific application areas, such as pipeline anti-corrosion (such as oil and gas pipeline inner and outer walls), steel reinforcement coating, valve coating, etc. The term “epoxy powder coating” is more widely used and is also commonly used for the coating of electronic components, automotive parts, power distribution equipment, and so on. Both belong to thermosetting epoxy resin coatings.

The thickness of the coating depends on the construction method.

• Electrostatic spraying: typically can reach about 40-250 microns (1.5-10 mils). If the workpiece is preheated before electrostatic spraying, a thicker coating can be obtained, even up to 1200 microns.
  
  
• Fluidized bed immersion coating: By preheating the workpiece and multiple immersion coatings, it is easy to achieve a thickness of several millimeters (such as 4000 microns or higher), especially suitable for occasions that require high insulation performance.

Some special formulations of epoxy powder coatings can be used for food contact surfaces, but they must undergo specialized testing and obtain relevant food grade safety certifications, such as complying with the regulations of the US FDA (Food and Drug Administration) or the European Union. Not all epoxy powder coatings are food safe. If it is needed for food related applications, it is necessary to choose products clearly labeled as “food grade” or certified by relevant authorities, and strictly follow the manufacturer’s instructions for construction and curing to ensure that the coating is completely cured and no harmful substances migrate into the food.

• Temperature: 180 ° C (356 ° F) to 200 ° C (392 ° F) is a common range, but some low-temperature curing powders can be cured at around 140 ° C (284 ° F), while high-temperature types may require higher temperatures. The important thing is that the temperature of the workpiece itself (Peak Metal Temperature, PMT) reaches the set value.
• Time: After reaching the specified workpiece temperature, it is usually necessary to maintain it for 10 to 20 minutes. For example, a common curing solution may be “workpiece temperature 180 ° C, hold for 15 minutes” or “workpiece temperature 200 ° C, hold for 10 minutes”.

Be sure to refer to the technical data sheet (TDS) of the specific product to obtain accurate curing parameters. Insufficient or excessive curing can affect the final performance of the coating.

The shelf life of epoxy powder coatings is usually 6 months to 1 year, depending on the manufacturer and storage conditions.

When storing, attention should be paid to:

• Low temperature drying: Store in a cool, dry environment, with ideal temperatures typically recommended below 25 ° C (77 ° F) and humidity below 50-60%. Avoid high temperature and high humidity, which may cause powder clumping or performance degradation.
• Sealed storage: When not in use, the container should be kept sealed to prevent moisture absorption and contamination.
• Avoid direct sunlight: Store away from direct sunlight.

• Orange Peel: The coating surface is uneven, similar to orange peel. The reasons may be poor powder melting leveling, improper solidification temperature, coating too thin or too thick, improper spray gun settings, etc. The solution includes adjusting the curing parameters, powder formula, and spraying process.
• Pinholes/Craters: Small holes or indentations appear on the surface of the coating. The reasons may be substrate contamination (oil, water), powder moisture, porous substrate releasing gas, and volatile substances escaping during solidification. The solution is to thoroughly clean the substrate, ensure powder drying, preheat and degas the porous substrate, and optimize the curing conditions.
• Poor adhesion: The coating is prone to peeling off from the substrate. The main reasons are improper surface pretreatment, substrate contamination, and incomplete curing. The solution is to strictly implement surface pretreatment processes, ensure substrate cleanliness, and ensure sufficient curing.
• Uneven Coating Thickness: The coating in some areas is too thick or too thin. The reasons may be improper operation of the spray gun, inconsistent spraying distance and angle, and electrostatic effects (Faraday cage effect). The solution is to standardize the operation of the spray gun, adjust the spraying parameters, and improve grounding.
• Particles/Impurities: Particles or foreign objects on the surface of the coating. The reason may be environmental dust, powder contamination, or insufficient screening of recycled powder. The solution is to keep the construction environment clean, ensure the purity of the powder, and regularly clean the recycling system.
• Faraday Cage Effect: It is difficult to spray powder on concave or corner areas. The reason is electrostatic shielding. The solution is to adjust the voltage of the spray gun, change the spraying angle, use a replacement gun, or select powder with better permeability.
  Solving these problems usually requires comprehensive analysis, starting from multiple aspects such as surface treatment, powder quality, equipment status, process parameters, and environmental control.