Defending Your Rooftop A/C Unit From Rust And Corrosion

Posted on: 27 May 2016

The biggest challenge faced by the average commercial rooftop air conditioning system involves standing up to rust and corrosion. In an environment dominated by high humidity levels, sea spray and salt-laden air, your A/C system will have a short and expensive lifespan unless it is adequately protected against these corrosive elements. Learn how the coastal climate can affect your rooftop A/C system and the ways you can fight back against rust and corrosion.

How a Salty Coastal Environment Affects Your A/C Equipment

In a typical coastal environment, the air contains a significant amount of aerosolized salts from the nearby ocean. These wind and water-borne salts can land on rooftop A/C equipment and make their way into the condenser coil, compressor and other various components. Over time, the chemical reaction of the salt with moisture and oxygen causes rust and corrosion to form on these surfaces.

Pitting and formicary corrosion can etch pinhole leaks into the refrigerant lines and the condenser coil, resulting in refrigerant loss and a corresponding loss of A/C performance. Corrosion can also damage the aluminum fins on the condenser coil and prevent latent heat from transferring from the coil properly. Rust can also damage the compressor, condenser fan and other A/C components.

Taking Preventative Action

Prevention is always the best medicine when it comes to caring for your A/C equipment. Fortunately, there are plenty of preventive steps you can take to safeguard your A/C equipment from the effects of rust and corrosion.

Cleaning the condenser coil on a regular basis can help remove corrosive salts along with dirt and grime buildup. Not only does it help prevent corrosion from forming, it also boosts your A/C system's efficiency by removing the dirt and grime that blocks airflow and interrupts the heat transfer process. According to Business Energy Advisor, power washing offers the best way of cleaning the condenser coil thanks to its ability to clean deep within the coil, whereas a typical cleaning with a soft brush only affects the surface of the coil.

Protective coatings can also be used to create a barrier between the coil surface and salt-laden moisture. The type of protective coating used depends on a number of factors, including the type of rooftop A/C unit used and the coil's heat transfer capabilities before and after the coating process:

  • Polyurethane coatings are thin, flexible and relatively inexpensive. However, they're not as durable as other coatings.
  • Phenolic-based coatings offer excellent resistance to heat and chemicals, but its thickness may reduce the coil's heat transfer capacity. It's also not as flexible as polyurethane coatings and it can't be applied on-site.
  • Silicon hydride or silane coatings resist water, scratches and offer an extraordinarily thin and flexible layer when cured. However, these coatings can be difficult and expensive to apply on-site.
  • Fluoropolymer coatings designed for on-site application offer excellent corrosion resistance, but the effectiveness of the treatment is short-lived when compared to other coatings. Fluoropolymer coatings done through electro-static powder coating or thermal sintering must be performed off-site.

You can also prevent rust and corrosion by mechanical means through the use of a sacrificial anode. Typically made from magnesium, aluminum or zinc, sacrificial anodes take advantage of differences between the A/C system's metal structure and anode's electrochemical potential, effectively causing the anode to corrode before the rest of the structure does.

If you're looking to replace your current rooftop A/C equipment, you may want to consider equipment that is designed with coastal environments in mind. These units often feature exterior cabinets made from stainless steel and other metals selected for their rust and corrosion resistance. The coils may also be treated for corrosion resistance before or during the equipment assembly process. For more information, visit a site like


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