In this blog, we will outline the top 7 things to know about shot blasting and powder coating.
Shot blasting differs from grit blasting because, as the name alludes to, the process uses spherical metallic abrasive, “shot”, while the other uses angular or sub-angular abrasive, “grit”. This slight difference is very significant. The abrasive’s shape (among other variables) changes the characteristics of the cleaning action and the workpiece’s surface profile.
Once shot abrasive strikes the surface of the workpiece, it dimples it, functioning under the principle of plasticity, while grit blasting’s sharp angular grains cut into the metal on impact, providing a rapid cleaning action and removing more material. Shot not only generates less dust than using angular media but also removes less material from the workpiece.
Moreover, shot abrasive is also used to “peen” surfaces. Shot peening is used on delicate machine components, such as gear parts or turbine blades, to relieve tensile stress and increase their compressive strength.
After the workpiece has been processed and the desired surface profile achieved, it is then sent to be coated. Powder coating is a surface finishing method that applies dry powder onto an electrostatically charged workpiece. Once applied, the workpiece is left to cure under heat or UV light.
Powder coating is typically harder and more resistant than solvent-based paint and is commonly applied to metal. However, UV-curable powder coatings can also be applied to MDF, plastics, composites, and carbon fibre.
The advantages powder coating has over conventional paint include is the fact that powder coating is environmentally friendly as it does not emit VOCs. In addition, compared to liquid paint, powder coating doesn’t drip, sag, or have a long curing time. Liquid paints long drying time also increases the risk of contamination during curing. Applying liquid paint is often more labour and cost intensive than powder coating because an undercoat and topcoat are required with a drying interval in between. Moreover, powder coating can be more economical as the excess unused powder can be reclaimed and reused.
“The benefits of powder coating mean it is used on a wide array of projects every day. In fact, powder coating represents over 15% of the industrial finishing market, according to the Powder Coating Institute. In fact, by 2025, it is projected that the industry will value $14.9 billion globally — up from just over $11 million currently — with China, India, and Southeast Asian countries leading much of the charge.”
Thermoset coatings are much more rigid and durable than thermoplastic. For instance, polyurethane thermoset coatings offer incredible weather resistance and are used to coat light poles and building facades. In addition, Polyester based thermoset powders are used to coat alloy wheels, which are exposed to some of the harshest environments as they must deal with road salt, weather, UV, and other contaminants.
However, thermoplastic coatings still provide excellent toughness and resilience to mechanical and chemical stress and are applied to items that will experience movement, such as handrails, fences, and domestic goods.