View our photo gallery

McElroy UniversityMetal Roofing and Wall Panel Coatings

The Importance of Quality Coatings

Coatings, or paint systems, play an important role when it comes to the overall performance of a painted metal panel. Since metal roofing and siding panels are continually exposed to nature's elements, care needs to be taken to ensure the coating system selected matches long-term performance and aesthetic expectations.

Offering quality coating systems to choose from is essential to McElroy Metal. Therefore, by choice and for the best performance options, Sherwin Williams, the industry leader in coil coatings, is McElroy Metal's coatings manufacturer.

Coatings consist of three primary ingredients: pigments, binder/resin, and solvents. Please read below to learn more about these three components and also about specialty coatings to meet a wide variety of design possibilities and environmental applications.

Pigments

Pigments are the coating ingredients responsible for color. Paint is created when the pigment is dispersed into the binder/resin. To further explain dispersion, think about a can of household paint. If you open a can of paint that hasn’t been touched in months, you will likely notice a layer of liquid on top of a more solid layer of material that has settled. The top layer of liquid is the binder. Before using the paint, you must disperse (mix or stir) the pigment into the binder again.

Pigments

Binder/Resins

The resin is what holds, or binds, the pigment together and protects the coating from UV degradation. Higher quality resins provide the greatest protection against panel chalk and fade. Conversely, coatings produced from lower quality resins are more apt to fade and chalk.  These failures occur when the binder breaks down and no longer holds the pigment together. 

The three most common resins for metal roofing and siding are Polyester, Silicone Modified Polyester, and PVDF (commonly known by the Kynar 500® trade name). These coatings also have a well-defined good, better and best performance rating. 

coating-chart

Resin Performance

Polyester coatings are considered low-end on the quality spectrum and are most often utilized for interior applications, such as liner panels or interior design accents.

Silicone Modified Polyesters (SMP) are an improvement over straight polyester coatings and represent a performance alternative between polyester and PVDF coatings. However, it is important to note that SMP performance simply cannot match the long-term performance of PVDF coatings, especially for darker colors. 

PVDF (Kynar 500) coatings provide superior protection against fade and chalk and are the industry standard for architectural applications. Quality focused manufacturers, like McElroy Metal, offer PVDF coatings across their entire product lines from post frame to pre-engineered to residential roofing. It is important to note that some manufacturers do not offer PVDF paint systems. If long-term quality is important, it's always best to ask questions about the coating early in your project planning.

Sherwin-Williams Product Comparison

 

Solvents

The third primary coating ingredient, solvents, is responsible for ensuring the paint has the desired viscosity to be properly applied. Solvents disperse the pigment. When the coating is applied, the solvent evaporates, allowing the resin and pigment to create the desired layer of coating and and be able to dry. In the case of metal roofing and siding, the solvent evaporates (burns-off from heat) during the coil coating process. 

Solvent for coatings page

Coil Coating Process

Once pigments, resins and solvents have been used to properly formulate the paint, the coating is applied to the metal coil. The coil coating process includes cleaning the metal coils and the application of both primer and top coats that are then cured with heat. McElroy Metal coils are coated by Precoat Metals and Steelscape. To gain more insight on the coil coating process, visit this Precoat Metal's link.

 

Coil coating process 

Specialty Products

Specialty Coatings - Prints

Advanced coating technologies have resulted in some exciting developments. Coil coated prints create multi-layered effects resulting in unique color combinations to create panels that can simulate slate, wood shake, COR-TEN Steel, wood grains, and camo. All McElroy prints utilize PVDF coatings, with the exception of Mossy Oak Camo which has a polyester coating.

Specialty Coatings - Environmental Specific

Harsh environments may require a specialty coating that offers enhanced performance over the standard PVDF (Kynar 500) systems. Coastal and chemically dense environments such as manufacturing with chemical discharge are two examples. McElroy Metal offers several Sherwin Williams specialty coatings to meet these types of severe environmental conditions.  

Specialty Coatings - Environmental Specific

Harsh environments may require a specialty coating that offers enhanced performance over the standard PVDF (Kynar 500) systems. Coastal and chemically dense environments such as manufacturing with chemical discharge are two examples. McElroy Metal offers several Sherwin Williams specialty coatings to meet these types of severe environmental conditions.  

Flurothane Coastal

Flurothane Coastal is a specially formulated PVDF coating for harsh saltwater environments and consequently is often specified for coastal applications.

Flurothane

Flurothane® PVDF coil coating systems include thick-film primers to give the metal substrate superb protection against the harshest industrial environments. In addition to ensuring a strong adhesion to the substrate, these thick primers also allow for superior adhesion of the topcoat, which provides even more protection of the base metal. 

 

Valshield

Valshield is a  PVC-technology coating designed as a durable coating ideal for applications that require great resistance in corrosive environments. Made of vinyl plastisol polyvinylchloride (PVC), Valshield offers great resistance to corrosion, abuse, and abrasion. Because of this, it works particularly well for buildings that are exposed to acid rain. While the coating is much more durable, Valshield is not a PVDF coating.  Consequently, panels are more susceptible to fade and chalk than Flurothane coatings.

Specialty Coatings - Environmental Specific

Benefits of High Performing Coatings

As indicated above, high performing  coatings are important when long-term performance and aesthetics are important. Warranties are also a consideration when selecting a metal panel. Consumers often associate warranty with dependability and performance.

This is not necessarily the case. Just because a warranty has an extended time frame (45 years or even a “lifetime”), it does not necessarily mean that the warranty is better or that the product offers better performance. We encourage you to fully read and understand your supplier’s warranties. 

Learn more about roofing warranties

Find a Distributor Near You

Speak to a Specialist

Substrate and Coating Articles on our Blog