Advantages of Powder Coatings
2012-06-07 Hits:
Advantages of Powder Coatings
There are several advantages of powder coating over conventional liquid coatings:
1. Environmental aspects
VOC: Powder coatings emit zero or near zero volatile organic compounds.
Environmentally friendly and energy and material efficient.
Powder coating production lines produce less hazardous waste than conventional liquid coatings. No paint sludge is produced, as arises from water-wash booths used to trap over-sprayed liquid paint.
Powder coated items generally have fewer appearance differences between horizontally coated surfaces and vertically coated surfaces than liquid coated items.
As Powder Coatings are solvent-free, no oven is required for the flash-off of solvents before curing.
2. Application and aspect:
Powder coatings can produce much thicker coatings than conventional liquid coatings without running or sagging.
One-coat application: a thicker, more uniform coating can be obtained by a single coating than can be achieved with wet paint.
A beautiful and uniform quality finish without paint runs.
A wide range of specialty effects is easily accomplished which would be impossible to achieve with other coating processes.
The electrostatic powder process ensures complete coverage, even on complex shapes (e.g., on castings).
Choice of finishes - clear, plain color, metallic or textured.
Exceptional gloss and color retention.
3. Technical aspects:
Corrosion resistance.
Robust mechanical and chemical performance - good at resisting abrasion, acids, solvents, etc.
Good electrical insulation capabilities.
Applicable to steel, zinc, brass and aluminum.
4. Productivity and Costs:
Powder coating overspray can be recycled and thus it is possible to achieve nearly 100% use of the coating.
Cost-efficient on small batches or single items, thus ideal for job coaters.
Quick turnaround times.
Ready to use: no stirring, mixing or thinning is required as it may be with liquid paints. Some application equipment enables the powder to be fed directly from the box
Fewer rejects: The ease of use of powder, both manually and with automatic application plant, gives a lower reject rate compared with wet paint. Rejects caused by damage after coating are also reduced due to the toughness of powder coatings
5. Capital equipment and operating costs
Capex for a powder line is generally lower than for conventional liquid lines.
Space requirement: less space is required than for liquid coatings equipments.
Ease of use: powder is far easier to apply than wet paint and less operator training is necessary
While powder coatings have many advantages over other coating processes, there are limitations to the technology. While it is relatively easy to apply thick coatings which have smooth, texture-free surfaces, 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 Tg (glass transition temperature) of the powder.
For optimum material handling and ease of application, most powder coatings have a particle size in the range of 30 to 50 μm and a Tg > 40°C.
For such powder coatings, film build-ups of greater than 50 μm may be required to obtain an acceptably smooth film. The surface texture which is considered desirable or acceptable depends on the end product. Many manufacturers actually prefer to have a certain degree of orange peel since it helps to hide metal defects that have occurred during manufacture, and the resulting coating is less prone to show fingerprints.
There are very specialized operations where powder coatings of less than 30 µm or with a Tg < 40°C are used in order to produce smooth thin films.
