Rust and corrosion are the implacable foes that ruin many a commercial AC unit. Rooftop-mounted AC units are especially vulnerable to this dastardly duo due to their completely exposed location. It doesn't take much for rust and corrosion to sideline an AC unit—exposure to sea air in humid, coastal areas and exposure to acid rain can damage and even destroy AC systems. Exposure to certain chemical and manufacturing processes can also accelerate an otherwise normal commercial AC unit's demise.
Formicary and pitting corrosion can slowly but steadily eat away at metal surfaces, leaving behind microscopic pinholes and tracks that cause refrigerant leaks and heat transfer problems. Rust formation on metal fans and other essential components can cause excess noise and even cause some components to seize up.
Prevention is always the key when dealing with rust and corrosion on commercial AC equipment. Here are a few preventive steps you can take to ward off the above problems.
Regularly Scheduled Cleanings
A professional cleaning remains one of the best ways to safeguard your commercial AC equipment against rust and corrosion. The cleaning process not only removes corrosive salts, acids, and other chemicals that could cause rust and corrosion over time, but it also loosens and removes accumulated dirt and debris from the coils. The end result is a system that's not just rust-free but also able to operate more efficiently.
An annual cleaning is usually all that's needed to prevent rust and corrosion. Additional cleanings can be scheduled as deemed necessary, especially after storms and other activities that bring potentially corrosive elements into contact with your AC equipment.
Protective coatings add a barrier between vulnerable AC components and the various elements that trigger rust and corrosion formation. A reliable coating can also prevent dirt and grime from damaging the coil and other protected components.
Protective coatings come in a wide variety of forms. Polyurethane coatings are the jack-of-all-trades—inexpensive, flexible and easy to apply in the field. Polyurethane coatings are also thinner than other types commonly used on commercial AC equipment. The only downside is that they lack the durability of other protective coatings. Epoxy coatings are similarly easy to apply in the field, but their relative thickness can present heat transfer problems that reduce AC efficiency.
Fluoropolymer or Teflon coatings offer exceptional resistance to a wide variety of acids, bases and solvents. Unfortunately, fluoropolymer coatings routinely suffer from poor adhesion when applied in the field. These coatings work best when applied via thermal sintering or electrostatic powder coating, similar to how non-stick cookware is made. Silane-based coatings offer excellent flexibility, water resistance, and excellent bonding to copper and aluminum. Like fluoropolymers, however, silane coatings are difficult to apply in the field.
The concept of a sacrificial anode is a relatively simple one. Instead of your commercial AC equipment bearing the brunt of rust and corrosion, a sacrificial anode made from a dissimilar metal with high electrochemical potential corrodes before the protected structure does. In essence, the anode sacrifices itself to protect the rest of the metal structure.
Sacrificial anodes are made from a wide variety of metals depending on the required application, but most anodes are made from aluminum, zinc, and magnesium. The anodes themselves don't need any external power to operate since the anode generates its own current. These anodes are usually installed over copper refrigerant lines and in close proximity to evaporator and condenser coils.
The only downside is that sacrificial anodes require constant inspection to prevent the anode from completely corroding away before it can be replaced. Once the anode is gone, your commercial AC system once again becomes vulnerable to rust and corrosion. An attentive commercial AC technician can prevent this problem from happening through regularly scheduled inspections of your unit.
Contact a company that offers commercial air conditioning maintenance services to learn more.