While some use the terms interchangeably, drying and curing are not the same. The two are distinct processes. Drying refers to the removal of water or a solvent by means of evaporation so that the final product is solid. Curing is a chemical process in which a polymer material toughens or hardens. Drying and curing happen simultaneously in several applications, like after the application of a protective surface coating on tanks. By knowing the science behind curing for surface coating applications, you’ll gain a greater understanding of how to optimize a tank surface’s ambient conditions.
Curing Basics
When you paint or coat an object, the material might be dry, but it may not be cured fully. When a coating is dry, it is no longer sensitive to local damage. A fully cured coating reached its ultimate structural integrity or hardness, fully adhered to a surface, achieved its maximum strength, and is stable enough for service.
During the curing process, a chemical reaction or physical action occurs, depending on the material. With epoxy polymers, for example, polymerization occurs when anhydrides or amines further polymerize prepolymers via the opening of epoxide ring terminals. The curing action creates a complex network of repeating units linked by linear ether groups.
Common Surface Coating Curing Methods
- Room temperature curing: Often used for RTV electro-plastic coatings or RTV elastomeric coatings, room temperature curing involves allowing a coating to cure in ambient conditions with proper ventilation. The moisture in the air aids the curing process when relative humidity levels are optimal.
- Mild heat acceleration: This curing method is similar to room temperature curing, as the coating cures in ambient conditions for a specific period. Afterward, workers expose the coated surface to warmer conditions, per the coating manufacturer’s recommendations. This method is not appropriate for solvent-less heat cure coatings.
- Heat curing: Best for solvent-less heat cure coatings as they don’t require moisture to cure, this type of curing exposes a coated surface to temperatures above 100°C in an oven.
- UV curing: A process that uses ultraviolet lights to induce a photochemical reaction that quickly cures a surface coating without the use of solvents. A polymerization reaction, rather than evaporation, cures the coating.
In regards to curing tank surface coating applications, it is important to keep in mind that curing processes often require specific air temperatures, surfaces temperatures, and relative humidity levels to dry and cure properly. Conditions that are too cold or too humid, for instance, tend to increase drying and curing times. Conversely, hot, arid conditions speed up drying times, but might not allow a coating to cure properly.
Contractors often encounter curing-related problems when they rely on the weather to cooperate rather than use Polygon’s temporary climate control solutions. The custom-designed solutions allow you to create the optimal environmental conditions needed to maintain a tank’s ideal surface temperature and promote predictable curing times. Proactive contractors that use climate control systems ultimately save money, stay on schedule, keep workers more productive, prevent costly delays and improve customer service. More importantly, the use of the equipment helps prolong a protective coating’s duration because it is cured properly during the application process. Contact Polygon to learn more about how climate control systems will benefit your current and upcoming projects.
[Photo from VIUDeepBay via CC License 2.0]
