Powder coating is a type of coating that is applied as a free-flowing, dry powder. Unlike conventional liquid paint which is delivered via an evaporating solvent, powder coating is typically applied electrostatically and then cured under heat or with ultraviolet light. The powder may be a thermoplastic or a thermoset polymer. It is usually used to create a hard finish that is tougher than conventional paint. Powder coating is mainly used for coating of metals, such as household appliances, aluminium extrusions, drum hardware, automobiles, and bicycle frames. Advancements in powder coating technology like UV curable powder coatings allow for other materials such as plastics, composites, carbon fiber, and MDF (medium-density fibreboard) to be powder coated due to the minimum heat and oven dwell time required to process these components.
Because powder coating does not have a liquid carrier, it can produce thicker coatings than conventional liquid coatings without running or sagging, and powder coating produces minimal appearance differences between horizontally coated surfaces and vertically coated surfaces. Because no carrier fluid evaporates away, the coating process emits few volatile organic compounds (VOC). Finally, several powder colors can be applied before curing them all together, allowing color blending and bleed special effects in a single layer.
While it is relatively easy to apply thick coatings that cure to smooth, texture-free coating, it is not as easy to apply smooth thin films. As the film thickness is reduced, the film becomes more and more orange peeled in texture due to the particle size and glass transition temperature (Tg) of the powder.
Most powder coatings have a particle size in the range of 2 to 50 μm, a softening temperature Tg around 80 °C, a melting temperature around 150 °C, and are cured at around 200 °C for a minimum of 10 minutes to 15 minutes (exact temperatures and times may depend on the thickness of the item being coated). For such powder coatings, film build-ups of greater than 50 μm may be required to obtain an acceptably smooth film.
Advantages of Powder Coating :
- The Color is Thicker. Paint technique powder coating produces colour that are more stable and thicker than other techniques. The thickness reaches 350 microns, while the thickness of oil paint is generally arround 30 – 40 microns.
- Hard Surface. In addition to the bold colour, the surface will be harder, thus making the metal or metal protection more scratch resistant.
- Stronger Adhesive Properties. The strong adhesive properties cause the powder to blend better with the metal. The chemical pre-treatment and the bake oven process up to 200 degrees Celcius resulted in the melting process of the powder being more integrated with the media.
- Closes The Pores Perfectly. The Powder Coating process is even the colour is thick. It will make the pores of the object completely closed. In contrast to oil paint, for a certain period of time there will be small cracks that are invisible to the nake eye, where over time these cracks can become a pathway for water, dew or steam to enter the pores which over time can trigger rust.
- Efficient. Powder coating is considered more efficient and economical compared to other techniques. The spread of colour can save the use of paint material directly.
- Environmentally Friendly. Media that uses powder coating is safe for health and very environmentally friendly. There are no special ingredients to dissolve the paint, which can peel off the paint and cause environmental waste. Even though the paints material is still in the form of wet powder, it does not cause a strong odor.
- Safety. Powder paint ingredients are safe for health, both for the respiratory, tract and skin if they are exposed to direct contamination. However, the use of security devices must still be necessary to reduce unwanted risks.
- Good Quality. The powder coating process at high temperatures and the rust removal techniques used before hand will create a good quality and corrosion resistant result. Objects protected with powder coating paint can withstand heat and rain far better than ordinary paint. The durability of powder coating can be up to 10 years.
Weaknesses of Powder Coating :
- It is difficult to find other colour dimensions that are more suitable, for example for this type of mettalic paint
- Can only be applied to Iron, Allumunium or metal. Can’t be used for rubber materials and can only be touched after the paint is dry
- The object to be painted must be completely sterile and free of seals of rubber because it will be heated to a temperature of 220 °C.