Comparison of Liquid and Powder Coatings:
(Liquid coating (i.e., paint) involves applying a thin layer of coating to a part. The coating must contain some form of solvent carrier that transfers the paint to the part being coated. The solvent carrier can be water or a chemical such as toluene or xylene. The solvent evaporates, leaving behind the thin film of coating. The coating must cure to form the final, hard finish. Curing can occur in one of several ways based on the formula: evaporation (air dry), baking (elevated temperature dry), use of Ultra-Violet radiation, or use of a catalyst.
By contrast, a powder coating does not involve the use of any liquid. A dry powder is electrostatically applied to the part, and then cured in a baking oven at a temperature of 350 to 425 degrees. There are no solvents to evaporate, eliminating all air emissions. There are no liquids required to clean equipment, eliminating all liquid waste generation.
Powder coatings have proven to be an efficient, economical, and ecologically sound method of industrial finishing. Generally, powders outperform liquids because of their higher molecular weight and greater insolubility; there is less film porosity with superior chemical resistance, toughness, hardness and abrasion resistance.
Some of the advantages of powder coatings include:
- Powder is an attractive choice over liquid finishing systems because it is a 100 percent solids material that contains no solvents. Powder coatings permit compliance with volatile organic compound (VOC) air pollution standards.
- Powder eliminates the need for storing flammable paints and solvents. And, there is no liquid paint sludge to dispose as hazardous waste.
- Oven exhaust and air make up can be reduced because no solvent fumes are emitted during the curing cycle. This results in considerable energy savings.
- Powder that is not deposited on the part can be reclaimed and reused, increasing material efficiency to as much as 95 to 98 percent.
- When a coating mistake has been made, powder can be blown off with compressed air and reapplied to the part before baking, further decreasing part rejection.
- The need for paint mixing is eliminated. Powder is introduced into the feed hopper directly from the box.
- Powder coatings can offer excellent color consistency, color matching capabilities and color and gloss retention.
- Clean up is easy; powder can be vacuumed off skin and clothing with a high efficiency vacuum.
- Soap and water will accomplish the final clean up.
While this all sounds too good to be true, there has historically been one limitation to powder coatings. They could not match the visual performance of a liquid coating. This limitation was eliminated within the past few years, when powder coatings have been developed to match liquid coatings in all measures of performance.