What is roll coating?

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By Richard Smylie | Apr 12, 2021
A sheet of metal going through a roll coater

From enhancing the visual characteristics of a part to shielding it from environmental damage, protective coatings have become a vital part of metal fabrication and finishing. While there are several different ways to apply a coating to metal, one of the most efficient and commonly used methods is roll coating.

Roll coating is the process of applying a base, intermediate, and/or topcoat coating to a flat substrate with a series of rollers. But how exactly does roll coating work?

What is the process behind roll coating?

Roll coating is a process that uses three rollers to apply a coating to a flat substrate: a soft application roll, a highly polished steel roll, and a metering (or doctor) roll. Firstly, the substrate travels between the soft application roll and the steel roll. The application roll picks up the coating as it rotates, and subsequently transfers the coating to the flat sheet of metal as it passes through. The metal sheets are then transferred to an oven where the coatings are baked and cured.

Roll coating offers a few benefits over other metal coating technologies. When applying a coating to a flat metal substrate, ensuring that the coating is deposited uniformly with the exact required thickness is critical. With roll coating, the amount and viscosity of the liquid deposited on the substrate can be precisely controlled by the metering roll. The closer the metering roll is to the application roll, the thinner the coating, and vice versa. This makes roll coating one of the most precise coating methods currently available.

Another reason why roll coating is so frequently employed is that its deposition time tends to be faster than other coating technologies, such as spray application or screen printing. In addition, the coatings used can help protect metal from harsh environments while enhancing ink adhesion prior to any embossing or other finishing steps.

What makes roll coating at GMN unique?

To meet a variety of project needs, GMN has two roll coaters; one that does direct roll coating, and the other that can do both direct and reverse. Reverse roll coating works roughly the same way as direct, the only difference being that the application roll rotates in the opposite direction of the substrate’s travel. Due to the different travel direction, reverse roll coating can apply a thicker coating than direct. This additional coating thickness is useful when the design intent requires a greater depth of color and environmental durability.

GMN’s coating family includes acrylic, polyester, and urethane coatings, each offering a different level of thickness, malleability, and resilience against heat and UV radiation. Each coating employed at GMN is custom formulated by our chemists to meet a wide array of project needs.

At GMN, we have years of experience using roll coating for products in a variety of industries, such as automotive, appliance, and personal care. To learn more about GMN’s custom roll coatings and how they can help your next project, schedule a consultation with our experts.