HVAC coil coatings are specialized coatings that are used to protect coils from corrosion and keep them running efficiently. The leading options in the industrial HVAC coil industry include: Polyurethanes, Epoxies, Fluoropolymers, and Silanes. When it comes to picking the right one for you, it's important to consider the variables that make each coating unique.
Polyurethane is an incredibly versatile material that was invented in the 1940s. It can be used to create a variety of different properties. Dr. Joshua Sole in his article A Discussion on HVAC Coil Coatings and Corrosion published on Reliableplant.com states that depending on how it is produced, Polyurethane coatings it can be as hard as fiberglass or being as bouncy as rubber, and even as sticky as glue or as soft as upholstery foam. Despite its versatility, polyurethane is also relatively inexpensive to produce and is less viscous, more flexible, and thinner than many other coatings. However, it is not as resilient or long-lasting as some other materials.
Phenolic-based, or epoxy coatings, developed in the 1920's, are an excellent choice for surfaces that require reliable chemical and heat resistance. However, due to their high viscosity, these coatings are difficult to apply in the field and result in thicker coatings that have poor adherence and flexibility characteristics. To ensure proper application, it is often necessary to send the coil to a professional for treatment. Unfortunately, this thick coating also reduces the heat transfer from air to the refrigerant in the coil, resulting in decreased system efficiency and capacity.
Fluoropolymer, popularly known as teflon, was developed in 1938 and is a popular choice for those looking for a durable coating. It has high resistances to acids, solvents, and bases, making it a great choice for those looking for a coat that can handle whatever comes its way. It is typically applied via electrostatic powder coating or thermal sintering, although field use sprays are also available for contractors. These field coatings are a convenient option, but do come with some drawbacks such as poor adhesion and a significant diminish in effectiveness over time. The cost of these field sprays is low, but the lifetime and effectiveness of the coating is limited. Applied properly with electrostatic powder coatings and thermal sintering these coats are top of the line. However, the inability to reproduce these processes in the field means that this coating is not always a popular option for HVAC contractors and technicians.
Silanes are a great choice when you need to bond two dissimilar materials together, such as organic and inorganic materials. They come in a wide variety of types, each with its own unique properties. For example, you can find silanes that form a glass-like coating, are flexible, and offer good corrosion resistance and water drainage. Additionally, if the right silane is selected you can get a incomparable bond to metals such as aluminum and copper. Once cured, they create an extremely thin layer that has minimal impact on heat transfer. Moreover, silanes are resilient against cracking and corrosion, are water resistant, and reduce airflow friction. Silanes can be applied in the field, but require extensive cleaning of the equipment to ensure a proper bond and are best done by trained applicators. Not every field agent may be up to the task. This coating tends to be on the more expensive end, but has a significantly higher lifetime and is well worth the investment, especially when considering the superiority of the heat transfer properties.
As mentioned above, many of these coatings can be applied in the field with varying degrees of effectiveness. However, we recommend ordering pre-coated HVAC coils to save with this hassle. Pre-coated coils are done by professionals with the highest quality in mind and will almost always out perform in-field coating work. This is especially the case when it comes to Fluoropolymer and Silane coatings. If you have questions related to HVAC coil coatings Re-Coil Solutions is here to help. We specialize in getting you the custom coil that will meet your needs. Give us a call today at 903-653-0942 and we will be happy to discuss you particular system's needs and the options available to you.