Coil Coating Explained: Your Ultimate Guide to Pre-Painted Metal Finishes

Okay, we’re doing some coil coating. You are running HVAC and that’s what you do in harsh environments: corrosion is a silent killer eating your profit and uptime. So, what is the play here, really? The best defense is coil coating, engineered to protect your valuable HVAC parts and seals its life…significantly, which prevents premature failure and saves you a lot of money down the road.

The Sneaky Attack: HVAC Coils and Corrosion

Ever stop to ask yourself why some HVAC systems just don’t hold up? It’s not so much about the build quality, as it is the battlefield they take to. The biggest culprit? Corrosion. We mean that slow, chewing metal monster that eats your tools alive and is the leading cause of breaking down your equipment.

Here’s where it hits hardest:

• Coastal: Salt spray from the sea takes no paws. And it’s not just confined to the beach; You can get hit with up to 10 miles of inflow, never mind the fact that a sizable portion of our coastline simply becomes a high-risk zone for HVAC equipment. Now picture that new shiny getting devoured in a year, says no one. That’s a bad look.
• Urban Jungles & Airports: City air isn’t only about mac trucks & yellow cabs, this also means that vehicle emisions are eating away at your coils. Airports, from their ever-present exhaust, are particularly brutal settings.
• Industrial Hot Zones: Got some factories nearby belching airborne chemicals? Or in proximity to wastewater treatment plants? These areas are the ground zero for the chemical attacks on your HVAC systems.
• Grease Traps Restaurants, particularly those with exhaust near rooftop HVAC units, emit cooking grease particulates that adhere to coils, forming a corrosive chemical cocktail.

But there are internal threats as well, beyond these environmental factors. Consider the galvanic corrosion that occurs when incompatible metals in the coil reactcate and destroy themselves. Plus, the process of pitting and formicary can cause leaks, which is a whole other headache.

So, What Are HVAC Coil Coatings, Exactly? Your Profit Protector.

In short, HVAC/R coil coatings are high-performance coatings that are specially formulated for application on heat exchanger coils of your heating, cooling, ventilation and refrigeration (HVAC/R) equipment. The mission here is relatively simple: stop corrosion. These are coatings that, in their most basic sense, establish a barrier around the coil, isolating it from the environment and its rotten corrosives. It’s actually all about protecting your essential assets to achieve peak performance with a longer service life.

The ROI: Coil Coating “Man’s Best Friend” for HVAC Maintenance

Adding coil coatings isn’t simply for prettiness’ sake—it really does pay off. We are talking about things you can measure that impact your bottom line and ensure your operation runs smoothly.

Here’s the breakdown:

• Triples Life of Equipment: This is not a marketing gimmick. A high-performance coating can at least triple a coil unit’s life. Think of using your gear three times as much. That’s massive.
• Saves Big On Energy Costs: The efficiency of a coil declines as it becomes corroded, causing your unit to work harder (burning more energy) and ultimately shortening its life. Coatings eliminate this and some decrease your energy bill by up to 30 percent. That’s also like finding free money in your budget every single month.
• Reducing Maintenance & Repair Expenditures: Not as much downtime needed to be allocated to inspection, repair, and replacing parts for system breakdowns; components don’t have to be replaced as often. It’s the ultimate preventative maintenance.
• Heat Transfer Losses: Here is where the magic happens. Ideal HVAC coil coatings are micro-thin: generally 1.4-ml thick or less. They’re designed that way to not interfere with the coil’s capacity to heat transfer. Like less than 1% loss in heat transfer. If a coating promises otherwise, move on.
• Lower Pressure Drop: Believe it or not, coated coils could lead to lower pressure drop than uncoated coils. Why? Because fewer contaminants will adhere to a slick, coated surface, which means less resistance to the flow of air.
• Protect Against the Nasty Stuff: In addition to salt, these coatings protect against UV rays, acid rain, emissions from vehicles in cities, and even microorganisms such as mold, mildew, E. coli, H1N1 and MRSA.
• Mix More Sanitizing Cleaning Solution: Stainless steel exceptionally easy to clean! This is enormous for public health and safety, especially in locations such as hospitals or food processing plants.
• Prevent Public Relations Disasters: No one wants equipment failure at a wastewater treatment facility or an airport. Coil coatings can help avoid these kinds of catastrophic failures, which can devastate entire communities.

Getting It On: How to Apply Coil Coatings

Ok, so you’ve bought into the “why” but how do these coats get applied to your coils? There are several main ways, each with their own pros and cons. Understanding the distinction is key to choosing the best approach for your project.

1. Spray-Applied Coatings

• How it works: As the name implies, the coating is sprayed onto the outside of the coil.
• Pros: Typically simple to apply and cost-effective. You can also purchase spray applied options from brands such as Heresite™ and BlyGold™.
• Cons: And here’s the rub – spray does not penetrate the inside of the coil, exposing some areas. Such coatings may also become more fragile and tend to flake off over time or as the coating is accidentally superimposed during mounting.

2. Immersion-Applied Coatings

• How it works: The coil is dipped in a bath of the coating.
• Pros: This technique provides uniform application and complete coverage of all surfaces, visible or otherwise. Certain new formulations are very long-lasting, and can even be compared to coatings which are applied electrically. Plus, some are also FDA approved for indirect food contact and are OEM-accepted. AmeriCoat™ and Ozkem™ are examples.
• Cons: More expensive than spray coatings over all, and one that requires more dexterity and experience than most.

3. Electrically Applied Coatings (E-Coat/Electrocoating)

• How it works: This is a multistage, carefully controlled process. The heat is exchanger pristinely cleaned. Next a DC charge is passed through the coil when it is dipped into a pool of oppositely-charged coating molecules. The layer is pulled uniformly onto the metal and creates homogenous film. This plating is self-limiting – once the coating reaches a certain thickness, the metal is insulated, and attraction slows to a balance point, resulting in even application. Finally, it’s usually baked in an oven in order to cure and cross-link the coating for the best level of performance. A UV topcoat may also be applied for extra protection. Very little is immune from Modine’s proprietary ElectroFin® coating.
• Pros: Bridging is kept to a minimum to enable the best coverage possible on all surfaces, especially deep cavities and the edges of cooling fins. It provides excellent protection in extreme conditions. It’s widely accepted by OEMs. Cathodic electrocoating, such as ElectroFin®, offers the best in corrosion and UV protection. It is also kind on the environment, containing low amounts of organic solvents and no heavy metals.
• Cons: Typically more expensive. Coils usually have to be sent out to a specialty vendor, which can add 1-2 weeks waiting for them to return. Note that not all of these formulations may be FDA-approved for direct food contact.

DYI Coil Coats: A Field Applied Reality

Where you have smaller coils or are up against a deadline you can’t afford to wait, then DIY aerosol coil coatings are a total game changer. They enable contractors to coil coat in their shop or at the job in place of shipping coils to a factory specialist.

Use this cord: On single condenser units, generally 10-tons or less. Ideal for a beachfront home where shipping to a specialist is impractical.

How it’s applied: The golden rule here is “clean” and “dry.”

1. Clean the coil: A foaming, non-acid, non-corrosive coil cleaner will be your best bet, but be sure to rinse it well. Even fresh coils can have machining oil remains that must be cleaned of good adhesion. For older, already-corroded units, use a special salt and oil-removing cleaner.
2. Allow to dry completely: You’ll need a completely dry coil before you can add the coating.
3. Mask the sensitive areas: You can mask the electrical contacts, moving parts and valves that you want to protect with blue painter’s tape. You may even choose to apply a layer of the dielectric to the compressor and accumulator for added protection.
4. Spray: From a distance of approximately 4 inches, here apply the coating in a manner similar to spray painting. Some are clear for an “uncoated” look, while others are blue to help you keep track of coverage.

Drying times: It is quick to touch (10 minutes), handle (20 minutes) and re-coat (30 minutes), but generally a full cure is 48 hours.

Re-application: Your coatings sacrifice themselves so you don’t have to, apply as needed for diminished throw. Depending on how harsh the environment, you may need to reapply every five to ten years.

The Straight Talk: Choosing The Right Coil Coating

When selecting a coil coating, a person is not guessing — they are choosing. The field is crowded, and not everything will measure up. You must ask the right questions and you must read the facts.

1. Independent Testing Results: Show Me the Data!

Don’t just trust marketing claims. ALWAYS ask for TDS sheets and independent testing.

ASTM B117 (Salt Spray Test) – This is a continuous test where a 5% Sodium Chloride solution is atomised at 35°C, it is still a non-cyclic test in that it’s always one thing or the other. While it’s widely used, ASTM itself recognizes the poor correlation (in most cases) between the test and the performance of a product as used. Nevertheless, plenty of coatings have reached 10,000-plus hours in this test.

ISO 12944-9: Cyclic Test This is the gold standard for offshore structures, and it is a lot more like real world. It’s a cyclic test, in that it simulates the cyclical exposure of a paint film to UV light, condensation, salt spray and even low temperatures. It lists 25 complete cycles (4200 hours). This standard is based on other standards such as ISO 16474-3 (UV/condensation), ISO 9227 (Neutral Salt Spray).

Other Key Tests:

• Chemical Resistant: Not everyone needs this, but if you are in an industrial environment or a lot of water locati0n, then looking for Chemical resistant markings will serve you well. Search for ISO 2812-4 or ASTM D1308/D4752/D5402.
• Harsher Salt Tests: ASTM G85 (SWAAT) or ISO 9227 (AASS) for more severe or acidic environments.
• Adhesion (ASTM D3359), Hardness (ASTM D3363), UV Resistance (ASTM G154), Anti-Microbial Activity: All essential to verify that the coating actually does what we claim.

2. Heat Transfer & Static Pressure:

• Good HVAC Coil Coating should cause minimal degrade in heat transfer loss, with less than 1% loss. An HVAC coil coating that is not made for your coils may be too thick, and not give you the efficiency that you need.
• Aim to find coatings that do not add to pressure drop, and in some cases could even reduce it by preventing the buildup of contaminants.

3. Hydrophobic vs. Hydrophilic:

• Hydrophobic (water-repelling): Typically, this is your best option. Moisture beads up and rolls off; the coil is nearly self-cleaning. It also helps to prevent “ice-bridging” on low airflow refrigeration coils.
• Hydrophilic (water-spreading): Highly spreading of water for an even distribution, beneficial in systems intended to remain wet, or where water spray is beneficial to heat transfer.
• Beware of coatings or non-engineered solutions that are not designed to consider water interaction.

4. Curing Method:

• Hot curing is typically favored for improved resistance and longer life over air dried films.

5. UV Light Resistance:

• Coil loops are often in the sun. Inquire about how the coating withstands UV exposure. Others have a top-coat or titanium binders for increased durability.

6. Aesthetic (Colour):

• Clear coats make the coil appear as though it is uncoated. Going to school Bus color coatings can assist applicators in monitoring coverage. Remember colour can have an effect on latent heat absorbed from sunshine – the darker the colour the more absorbed, and the lighter the colour the more reflected.

7. Request a Sample:

• Don’t just look at brochures. Then, request a typical painted coil sample. This helps you judge the actual finish feel, smoothness and pressure to ensure it meets what you expect for both feeling and appearance. Any old scrap of fin material won’t do — you need to see how it works in a complex coil.

TIme to Name Names: The Major Coil Coating Players

The HVAC sector is supported by several prominent players that are recognized for their successful coil coating solutions:

ElectroFin®: This is Modine’s proprietary cathodic electrodeposition epoxy coating. It is micro thin (0.6 – 1.2 mil), has excellent corrosion resistance and utilizes high edge build technology, extremely important for micro channel condensers. To date, they have more than 100,000+ micro-channel coated condensers around the world.

Energy Guard: Their EGuard Fin Primer allows for superior adhesion and the DCC Green and DCC Aluminum coatings are 30% aluminum and salt spray tested for 10,000 to 12,000 hours.

Heresite®: Provides solutions such as P-413 Baked Phenolic Epoxy, thin-film exotic coatings with high performance properties that match the demanding ISO 12944-9 standard for harsh offshore marine settings. They also produce HereShield (WB-506), an air-dry, water-based coating.

Blygold: Specializing in the development of HVAC protection against corrosion. Their PoluAl XT is a aluminium pigmented urethane that has superb chemical and UV resistance, flexibility and adhesion. They also provide PoluAl™ WB, a water-based formula with corrosion-inhibiting properties and high aluminum content. The Blygold range of coatings are formulated to seal the heat exchanger without sacrificing heat transfer or pressure drop. They even promise to triple lifetime and save as much as 30% on energy costs.

FinKote Series:

• FinnKote2: a premium high edge e-coat solution for maximum adhesion to aluminum, copper and steel microchannel and tube-and-fin coils. It guards against intense UV exposure and harse conditions.
• FinKoteRx: 99% anti-microbial that prevents, I want to say… mold, mildew, E. coli, H1N1 and MRSA.
• FinKoteZx: A multi-coat system provides extreme protection in severe environments such as food processing plants, wastewater treatment plants and refineries, often NSF-51 Certified and FDA Compliant.

Joining Forces Smart: How to Work with Coil Coating Applicators

You’ve chosen the coating; so how do you get the best deal and ensure the process is a smooth one? It’s all about helping your coater run an efficient business, and that’s money in your pocket.

• Batch Your POs for Oven Capacity: If your coating requires heat cure, the oven is the largest energy user. If you can submit quantities that fill a company’s oven, they can give you a break on the price, so you should give yourself a break, too.
• Think Blanket Purchase Orders (POs): You quote a blanket PO for a period up to one year. This enables your vendor to anticipate demand, control raw material inventories (which can be costly and take months in delivery), and schedule production effectively. This translates to, for all, on-time delivery and better cost control.
• Provide Stock Keeping: When possible, allow your supplier to hold their inventory in their warehouse to coat while they are slow. A reliable work line is efficient for all manufacturers and you should be willing to negotiate a discount for that kind of work load if you are being flexible on completion times. When you have predictable workloads, you can build efficient factories.”

Bottom Line: Your HVAC Investment Warrants Coil Coating

I mean let’s face it, with the challenging environments we are exposing our metals to and longevity we’re demanding from our machines, coil coating isn’t a luxury it’s a must. It is no secret, which is why nearly every major HVAC/R manufacture now using coated coils inside their equipment.

Why? Because it simply works. It’s keeping all your assets secure, making them last longer, saving you a big pile of money in energy and maintenance and helping you get the most from your systems. It’s a wise move for anyone really concerned about both the longevity and efficiency of their heating and cooling gear.

FAQ: Coil Coating in a Nutshell

Q1: What exactly does coil coating do for my HVAC unit? A1: A protective coating on your HVAC coils to prevent corrosive damage from harsh environments – such as salt spray, urban pollution, and industrial chemicals. This protection means a lot fewer breakdowns over time and a longer lasting system, and there’s a lot to be said for that – including for energy efficiency.

Q2: How big of a deal is corrosion on HVAC coils? A2: Absolutely. HVAC coil corrosion is a leading cause of coil failure and diminishes the efficiency of your equipment which can result in higher energy bills, increased maintenance costs, and shortened system life. Atmospheres such as the coast, cities and industrial areas may corrode in just one year.

Q3: What’s the true value proposition — in dollars and cents — of coil coatings? Q3: The savings can be big. High-quality coatings can extend a coil unit’s life by more than a factor of three. And they can result in energy savings of as much as 30% by improving heat transfer efficiency and decreasing pressure drop. Other areas where you can pass the savings on would be costs for inspections, repairs and replacement parts.

Q4: How is a coil coating best applied? Q4: What are the primary ways in which paints and coatings are deposited? A4: Spray, immersion, and electrically applied (e-coat). E-coat provides the best coverage of any protection for all coil surfaces, while also being a effectively coating hard to reach areas. They can be durable and also offer even coverage prospect as immersion coating. Least expensive are spray coatings, but they don’t cover all surfaces.

Q5: I want to put a coil coating on by myself. A5: Yes, there are DIY aerosol coil coatings for smaller units (10-tons or less). They’re cost-effective, and can be made in your shop or on-site. The most important are the targeted placement of the “clean” and “dry” coil, protecting sensitive areas and adequate drying opportunity.

Q6: Does the performance (heating/cooling capacity and efficiency) of the unit depend on coil coatings? A6: Good quality HVAC coil coatings are formulated to not lose heat transfer – loosing less than 1 percent. Inspired by the design of some Japanese drugstore brands, they’re made to be miracle-thin (1.4-ml or less) for maximum heat exchange. They can even reduce pressure drop slightly by helping to keep the coil surface cleaner.

Q7: What is the life of coil coatings? Do we need to re-apply it? A7: Depends on the environment and the type of coating, but they are sacrificial, so they take the corrosive beating rather than the coil. Frequency of re-application may be in 05, unfortunately we cannot say right now how long it will need to wait before re-applying, but if you re-seal it every 5 – 10 years, depending on how harsh the environment is.