Powder Coating vs Liquid Paint

Liquid Paint vs Powder Coatings

Introduction to Liquid Paint & Powder Coatings

Surface finishing is what gives workpieces their unique visual properties. Typically, these surface finishes will offer some functional surface protection to the workpiece as well. Coaters often must choose between two established coating systems: liquid paint and powder coatings. Powder coatings have become increasingly popular in recent decades, partially due to an increased focus on sustainability. Depending on an applicator’s requirements, both technologies offer individual advantages and disadvantages. The following article will highlight the similarities and differences between liquid and powder coatings’ composition, application, cure conditions, appearance, durability and mechanical properties, and environmental sustainability.

Paint Composition

Liquid paint is a mixture composed of non-volatile components (binders, additives, pigments, fillers) and a volatile component (solvent). During the curing process, the volatile liquid solvents begin to evaporate, allowing the remaining paint components to form a dry film. On the other hand, powder coating is a dry mixture in which the resins, additives, pigments, and fillers are essentially milled to form a fine powder. 

The primary difference in the composition of these two paint types is the inclusion of volatile liquids in liquid paint chemistry. Furthermore, an additional difference between the two is powder coatings are a completely dry product without any suspending liquids used during manufacturing or the application of the coating – this also contributes to why powder coatings are considered the environmentally friendly alternative to liquid paint chemistries. 

Paint Application

Liquid Paint

Liquid paint can be applied in many ways. Job and finish requirements often determine the most applicable application type: 

  • Smaller job requirements tend to utilize brushes, rollers, and manual spray guns in the application of liquid paint. 
  • In larger-scale liquid paint application environments, such as manufacturing sectors, automated spray guns, and rotary bell devices become more common for the improved speed, consistency, and efficiency they offer. Electrostatics are often used in these larger application types to help further increase paint transfer efficiency.
  • Another liquid application method is dipping. In this process, workpieces are submerged in a paint bath. This method is suitable for coating components that are otherwise difficult to coat due to their shape or size.

 

Powder Coatings

Powder coating is most commonly applied through “Electrostatic Deposition,” which often utilizes spray guns. The workpiece must show electrical conductivity since the powder adheres to the component by electrostatic (or tribo-static) charging. 

In special cases, other special application variants are also used:

  1. Hot Flocking: By heating the substrate, the powder is melted directly on contact and thus collects and adheres to the surface. The powder can be applied either by spray gun or by fluidized bed application.
  2. Application of conductive liquid: Creates the conductivity required for powder coating, so that even originally non-conductive substrates, such as plastics, can be coated. 

As a result, it is now possible to coat a wide range of non-metallic substrates (plastics, glass, ceramics, etc.) with powder coatings.

Paint Cure Conditions

The curing process for liquid paint takes place with the evaporation of the solvents and [once?] the polymers have cross-linked. This process can take place in an oven, or, with certain resins or waterborne paints, can be the result of air drying. Liquid paint solid percentages vary but can range from under 30% to greater than 60% – whereas powder coatings are 100% solids. Solids ratios affect the coverage produced (lower solids equal less theoretical coverage). Liquid finishes often require several coats to meet film thickness requirements – resulting in an increased processing time of several hours, or potentially a few days. Also, to assure safety, workers must wear protective equipment and the workplace requires proper air circulation since the evaporating chemicals are harmful to human health.

Comparatively, the powder coatings curing process offers efficiency due to the time saved during application: For most applications, only a single layer of powder coating is required, and this single layer provides a superior finished surface. After application, the powder coated parts are placed in the curing oven and the powder is melted and cured employing a chemical hardening reaction. The required curing time depends on the composition of the powder coating and the nature of the workpiece. Once cooled, the coating is ready for immediate use. A properly fitting dust mask is all that is required within the application environment to keep the applicator safe.

Typically, the curing temperatures for powder coatings are in the range of 160-200 °C, which initially limited the types of substrates that could be finished with powder coatings. However, new developments in powder coating technology have and continue to significantly lower cure requirements, allowing for greater flexibility in substrate selection. For instance, t is already possible to coat wood-based materials such as medium-density fiberboard (MDF) or even individual solid wood pieces.

Finished Product Appearance

Products finished in liquid paint predominantly produce products with very smooth and vibrant finishes. Due in part to the addition of solvent, which directly influences the flow properties of liquid paints, it is easy to produce a very smooth finish with liquid paints. Moreover, liquid paint systems stand out with vibrant effects, such as bright metallic finishes, as the orientation of the metallic effect pigments can be easily aligned for maximum visual effect during the solvent evaporation process.

Equally, powder coatings have developed rapidly in terms of product diversity and visual effects. Over the years, various products such as metallics, flip-flops, dormant pigments, pearlescents, and many more have been developed and are continuously being improved. Now, powder coated products offer an array of finishes, effects, and colors.

Durability & Mechanical Properties

Compared to liquid paints, powder coated surfaces offer improved functionality in scratch and impact resistance, deformation resistance, and polymerization. The result of this improved durability is the reduction in the cost of ownership, by offering better substrate protection, and reduced frequency of repair. 

Additionally, Increased film thickness, which is another property of powder coatings, results in better edge coverage of coated parts, which, in terms of corrosion protection, makes powder coatings superior to commercially available liquid paint finishes.

Environmental Sustainability

One area in which powder coatings are especially superior to liquid paint is environmental sustainability. When liquid paints are cured, the solvent evaporates vapors known as volatile organic compounds (VOCs) are released into the air. These chemicals are both a concern for human health and harmful to the environment. For liquid paints, additional care during application is necessary, which if not addressed can result in wasted product, and the cost of disposal of liquid paint can be expensive. First, care must be taken to avoid defects in color, due to improper settings of the spray guns and rotary bells, which may result in wasted paint and finish defects. Liquid paints cannot be recycled during application and liquid painting applications are spray-to-waste applications since the paint that does not attach to the workpiece cannot be reused. The overspray must be collected and disposed of either by hazardous landfill space or incineration. The typical transfer efficiency for liquid paint is approximately 30%-40%. By comparison, powder coating transfer efficiencies can range from 90-95% with state-of-the-art powder coating equipment, resulting in less material wasted and greater environmental sustainability.

Across the entire value chain, powder coating offers a lower overall carbon footprint compared to solvent-containing liquid paint chemistries – this calculation accounts for the total embedded carbon within raw material inputs, manufacturing processes, and the application of the coating – which surmounts in powder coating being exceedingly more environmentally friendly and sustainable.

Conclusions on Liquid Paint vs Powder Coating

It is not possible to proclaim which paint technology is "superior," as each workpiece has different requirements depending on the desired surface finish. Liquid coatings offer certain benefits for metallic effects and a wider array of application substrates, while powder coatings offer improved application efficiencies, superior mechanical and durability properties, overall health and safety benefits, and environmental bonuses and considerations. Therefore, it is up to the individual to evaluate what is the superior paint type for their personal and product requirements.   

TIGER Drylac’s Superior Powder Coatings

If you are in the market for powder coating products or intrigued by some of the benefits listed above, consider utilizing TIGER Drylac’s products. TIGER Drylac offers an extensive array of high-quality powder coatings for any interior or exterior project or product. 

TIGER has always been at the forefront of powder coating developments, pioneering much of the powder coating technology. Most recently, TIGER Drylac introduced 3D metallics in 2017, subsequently revolutionizing metallic powder coatings by raising the visual impact of metallic powder coatings. This new 3D technology allows designers to offer surfaces with comparable depth and effect to liquid paints. Furthermore, TIGER offers a variety of textured finishes that are unavailable in liquid finishing.

If you are interested in learning more or purchasing TIGER Drylac products, head to our website or click here to view our webshop.

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