When asked about the differences between powder and liquid coatings, Bill Lemons, technical manager with AkzoNobel, ran down the details.
Powder coating advantages
- Volatile organic compound (VOC) content is generally lower than the majority of solvent-based liquid coatings. Solvents are not required to keep the paint in liquid suspension form, nor are they used to adjust viscosity or modify flow characteristics in the final film.
- The dry film thickness of powder coatings tends to be much higher than liquid coatings and can be applied without runs, drips or sags. The higher film builds can be advantageous in certain applications, such as underbody parts and areas where stone chipping, etc. are prevalent.
- The overspray in powder coatings can be recycled, which improves the overall transfer efficiency and paint consumption rate. Powder coatings tend to have very good long-term storage stability.
Powder coating disadvantages
- Specialized electrostatic spray equipment is required for application and the surface must be conductive to accept the charged paint particles. This limits the ability of powder coatings to penetrate well into parts that have deep recesses.
- All powder coatings used in industry must be baked in an oven; ambient cure is not an option. Continuous, thin paint films of 1 mil (25 microns) or less are difficult to achieve with powder coatings. Changing out colors in a production environment is slow and cumbersome. Orange peel readings can be higher than in liquid coatings.
- Powder coatings cannot be mixed with each other to obtain different colors, therefore mixing-machine/toner systems such as those used in liquid paint technologies are not an option. All powder colors must be produced to the final color match at the paint supplier’s factory.
Liquid coating advantages
- Low VOC products are available, allowing you to bring some liquid coatings products into regulated areas.
- Liquid coatings can be applied at lower film builds, which means less coating is required, which can be an economic advantage.
- Ambient cure is an option in some liquid paint technologies, so no oven is required. Ambient cure coatings also allow you to tape off sections of the part to prevent them from being painted, which can be necessary during repair operations or when creating custom color designs on vehicles.
- A wide variety of substrates can be painted with conventional liquid paints and the substrates do not need to be conductive for the majority of applications. The substrates must be properly prepared to accept paint, and the substrate must be compatible with the paint.
- A wide variety of color variations is available from a single toner mixing bank, and it is easy to switch between colors in a production environment.
Liquid coating disadvantages
- Many liquid coatings are fairly high in VOC, which limits their use in regulated areas. Significant training and hands-on experience are required to become a fully competent painter in liquid spray applications.
- Spray booths with sufficient ventilation and other capital expenditures are necessary to use the products in a controlled, clean, and safe environment.Also, insurance costs to use and store solvent-based paints and flammable solvents and paints are high.