Powder Coating – What is Powder Coating?
Powder coating is applied as a free-flowing powder in a completely dry form, think of it as paint without solvent that is applied on metal which is then cured under specified heat.
It can be categorized in three main forms, thermosetting, thermoplastic and UV curable powder coatings. It provides high quality protective and decorative finishing.
Powder coating is one of the most advanced coating processes which provide ultimate finish durability and long life.
The Process Are:
Baking at High Temperature
Materials Commonly Used:
Epoxy Powders – They have excellent chemical resistance, solvent free but poor tolerance to heat and light
Acrylic Powders – Provide good gloss and good color retension on exterior exposure.
Polyester Powders – Excellent durable and a high resistance to yellowing under ultra-violet light
Epoxy Polyester Hybrid Powders – Have improved resistance to overbrake yellowing and improved weathering. Hybrid powders are now regarded as the main backbone of the powder coating industry.
Polyurethane Powders – Provide good all round physical and chemical properties as well as giving good exterior durability.
Powder Coating Application Process
The exact method depends on size and type of material from surface preparation to finishing stage. The powder coating process begins from removing dirt, oil, grease, dust – from solvent cleaning to high pressure water washing to blasting from the steel surface.
The powder can be applied onto a preheated substrate (in the case of substantial steel thicknesses) at about range from 180oC 240oC, for about 10-15 minutes which is electro statically applied and post heated.
Powder coating is electrostatically applied, which is the most common way.
The final step is curing the metal at a given temperature to further strengthen the material.
In either case the powder melts, undergoes a chemical reaction and in approximately three minutes the reaction is complete depending on environmental conditions.
What is The Benefit of Powder Coating?
Moreover, powder coatings are available almost in all ranges of color and textures.
Easier application method
Mostly it is single coat system
99.9% solid, no solvent or water required
No primer required
It can be reclaimed
No skilled labour required
Mainly, it is cost effective, environmentally friendly, highly tough no matter which application process is utilized, powder coating is easy to use.
The coated surfaces are highly resistant to scratching, fading, chipping, wearing than other finishes.
Powder coated products are more resistant to diminished coating quality as a result of impact, moisture, chemicals, ultraviolet light, and other extreme weather conditions. In turn, this reduces the risk of scratches, chipping, abrasions, corrosion, fading, and other wear issues.
It’s tough. It looks great. And it lasts a long, long time. In addition to being durable, powder coating is an attractive choice due to environmental advantages.
Disadvantages of Powder Coating
Thin films such as 25 microns are difficult to apply as compared to liquid paint.
Compared to liquid paints, color changing is much slower
Since unused powder particles are collected and reused there is a risk of cross contamination.
Powder coating is not good at achieving a smooth finish
Requires to construct a special booth and rely on an expensive oven in order to complete the process.
What Temperature is Needed for Powder Coating?
Follow the manufacturer recommendations for the exact temperature and curing as it can vary on different materials.
Moreover, there are other factors which include the size and mass of the object, along with the efficiency of the oven and thickness of the coating applied.
It’s important to cure the metal at the appropriate temperature so that it will provide a uniform and durable finish that to last for years.
Powder Coating Application Issues
During application ensure the settings of the gun, film build, gun to part distance. Ensure the equipment is well maintained.
Poor Charge, Low Film Build, and Insufficient Wrap
Powder flow shall be controlled as incorrectly kV levels can negatively affect the application process.
Ensure to have good earthen ground.
What are Coating Defects?
Film thickness and coverage can truly affects the overall finish of the coating. In case of too high thickness, one will run into issues like orange peel or sagging.
And too thin thickness will not cover the surface well which will lead to pinpoint rusting instantly.
Here are Some Commonly Faced Powder Coating Defects: