Liquid or powder coating: which one to prefer and why?
Have you ever wondered what advantages a powder coating brings over a liquid one? Read on to clarify any doubts.
Right from the first phase, it is necessary to be clear about the end use of the item and consequently choose the correct materials and coatings to avoid nasty surprises. Coating a surface means improving it aesthetically and protecting it from wear, chemical agents, and weathering.
Powder coating is the process used to coat metal materials with a thin film of powder coating based on synthetic resins. The powder, previously negatively charged using an electrostatic gun, is sprayed onto the grounded metal surface to ensure perfect adhesion. Innovative technologies now also make powder coating of glass, ceramic and MDF artifacts possible.
Liquid coating is a process used to coat varied materials with a liquid film that loses solvent during the film-forming phase until it reaches the required polymerization level. Depending on the formulation technology, the film-forming phase requires a later cross-linking phase that can take place through the action of UV light, second components, or by simple remodelling of the original polymer. Liquid coatings can be applied in a variety of ways, from the most manual systems (brush) to more advanced and complex systems (e.g., robotic spraying, rollers, curtain coater).
Which is the best choice between powder coating and liquid coating?
We at RIPOL are convinced that, for metal protection, powder coatings offer far greater competitive advantages than liquid coatings. That is why we focus exclusively on the production of powder coatings, products that allow us to respect the environment and guarantee our customers a high-performance coating.
Increased resistance and durability
Powder coatings are ideal for metal substrates as they have a high resistance to UV light, weathering, and aggressive chemicals. A powder coating provides a thicker, homogeneous layer than can be achieved with a liquid coating and, as a result, it is not only more durable but also highly resistant to chipping, abrasion and scratching. Powder-coated substrates can last for decades.
The use of powder coatings also guarantees excellent edge coverage and the absence of any leaking spots in the coating.
Less coating waste
In the powder coating process, a recirculating powder that does not adhere to the substrate can be recovered with the use of suitable equipment, mixed with the virgin product and reintroduced into the coating cycle. This guarantees a reduction in overspray with an overall use of 95% or more.
During the film-forming phase, liquid coatings can lose up to 90% in weight with a high rate of volatile particles dispersing and, in the case of solvent-based coatings, VOC emissions. In addition, overspray cannot be recovered.
Reducing overspray during powder coating results in less waste and consequently lower costs.
Environmental regulations concerning the dispersion of hazardous materials, such as solvents, require a quite onerous procedure to be followed in the management of emissions throughout the application, drying and residue disposal process. Producers and users of liquid coatings must be equipped with special burners capable of removing solvents or abatement filters, take compulsory safety measures for the presence of flammable liquids and set up a disposal plan for hazardous waste. Unusable powders at the end of the coating process also require dedicated disposal but, due to the absence of solvents, the costs are significantly lower than liquid paints.
Even in comparison with water-based liquid coatings, the powder coating solution has different costs and efficiencies that must be considered. Although water-based coatings have a lower VOC content than solvent-based ones, they require careful management of humidity, temperature and ventilation during application and drying.
When drying liquid coatings, the air exchange in the ovens is extremely high compared to powder coatings. This results in a decrease in thermal efficiency, safety level and, of course, a higher VOC reduction cost.
Liquid coating, unlike powder coating, requires a mixing phase with other products (thinners, second components, accelerants, etc.) before use. This phase must be conducted carefully to avoid mistakes that could lead to defects in the final appearance of the workpiece. Furthermore, unlike liquid coating, which involves a solvent evaporation time and a drying time, powder coating only involves the polymerization phase. A huge time saving and, consequently, higher productivity with the use of powder coating.
Respecting the environment and reducing pollution
Powder coatings are the ideal solution for those who respect the environment: they contain no water, no solvents, no Volatile Organic Compounds (VOCs) are released and they are heavy metal-free. In addition, as they do not contain pollutants, they pose no threat to the health of operators either during production or coating.
Some kinds of liquid coatings contain solvents and are therefore highly polluting. Furthermore, very often, these types of coatings continue to emit VOCs even after application, resulting in the phenomenon of so-called indoor pollution. Water-based liquid coatings, on the other hand, while much less polluting than solvent-based ones, have a water content of more than 70 percent.
Ease and speed of application
Although powder coatings can only be used with industrial equipment, they are easy to apply, do not have to be spread and do not drop. In case of damaged areas before curing, the powder can be removed with the simple use of a compressed air gun and then applied again. In addition, powder coating involves fewer steps than liquid coating, thus enabling faster processing.
Finally, an important level of accuracy and experience of the coating contractor is essential for a successful liquid coating, while powder coatings require no special operator training.
Do you still have doubts about using liquid or powder coatings on metals? Do you need further clarification? We are here to help you, contact us and we will clarify any further doubts.