The AC system endures a lot of wear and tear, modern units tend to be more durable, but they still need regular servicing to work at optimal efficiency. Moisture can lead to the formation of rust which can spread quickly throughout the system. This looks bad, but beyond the surface ugliness there are other problems and the components can deteriorate. This can lead to premature failures and expensive repair bills. In this article, we will examine the causes of corrosion and some ways to deal with the problem.

What Causes Rust?

Before we get started, here is a brief primer on how rust is formed. Rust is created when metals such as iron and steel are exposed to a combination of water and oxygen for a certain period of time. The first signs are small dots of rust, but they can spread quickly and eventually coat the entire surface of the metal. There are AC components that are especially prone to rust damage. They are the air filters, coils, the compressor, fan blades, ductwork, refrigerant lines, and the drain pan. Now let’s take a look at the four most common causes of rust in AC systems.

1.  Excessive Levels of Moisture

This is the most common source of rust problems, the moisture could come from condensation, exposure to rain, and even very humid air. During regular operation, warm air is drawn into the system from outdoors for cooling and the moisture in the air condenses on the evaporator coils and then ultimately drips down into the drain pan. This process is entirely normal and your AC system is not affected in a negative way. But, rust problems can develop if that moisture remains in contact with AC components over a prolonged period of time. This can happen if the drain pan or the connecting drain line is clogged and the water overflows around and into the AC unit. People living in coastal areas may notice corrosion on their outdoor units because the air is salty and humid. An outdoor unit crowded with plants can be affected, if it’s in contact with wet leaves and chemical fertilizer products that corrode the metal surfaces. When rain falls directly on the outdoor unit, it can hasten the formation of rust too.

2.  The Age of Your AC System

AC systems are limited to a finite lifespan of 10-15 years and the formation of corrosion is a natural part of that process. When a system is reaching the end of its useful lifespan, the regular wear and tear accelerate. It’s normal to notice certain problems, such as strange noises, rising energy bills, lower airflow, and the formation and spread of rust.

3.  Volatile Organic Compounds (VOCs)

These are compounds that are found in a wide variety of products, including paints, air fresheners, household cleaners, and more. If VOCs are present in the indoor air, they can enter and are recirculated by the AC system. These compounds are harmful to metallic surfaces and the most obvious example is the corrosion caused to copper tubing that carries the liquid refrigerant. This will cause refrigerant leaks that can degrade the performance, lower the energy efficiency and damage the components.

4.  A Lack of Regular Maintenance

All HVAC systems are complex, they require regular maintenance and if this need is ignored for too long it will lead to poor performance, inefficiency, and even a shorter lifespan. Regular maintenance will detect moisture and debris that cause the development of rust. When air filters are dirty this can make the coils rusty and a clogged drain pan can create water leaks which may lead to rust problems. The outdoor unit needs regular cleaning to remove dust, dirt, debris, and moisture that can clog the system and create rust.

How Can I Prevent Rust in my AC System?

If you notice a patch of rust forming, it’s important to take early action before the problem worsens. Here are eight tips to prevent the formation of rust in the AC unit:

1.   Mini-Split Units

The focus should be purely placed on a preventative HVAC maintenance program. An HVAC technician can inspect, clean, and repair your mini-split units to improve performance and efficiency. During the cleaning, they will remove any debris, dirt, and moisture that could cause rust problems.

2.   Check the Outdoor Unit

The outdoor unit is designed to withstand a wide variety of weather conditions. But, it’s a great idea to check it periodically to see if any debris, leaves, or other materials are stuck on the top or side of the unit. The area around the outdoor unit must be clear of obstructions to perform efficiently. Vegetation should be trimmed back and if the area is clear there is a reduced chance of rust because there will be less moisture.

3.   Check and Clear the Drain Lines

When excess moisture mixes with dust and debris, it can form a clog in the drain lines. This will cause the drain pan to fill to capacity and then the water will overflow. This can cause water damage and the formation of rust in and around the system. The drain line can be cleaned with a long wire bruise and bleach should be poured down every six months to prevent mold growth.

4.   Coil Maintenance

The AC coils should be cleaned every two months with a soft brush and a homemade or commercial cleaning product. To make your own cleaner add mild dish soap to a bucket of water and add a little baking soda for gentle abrasion. Use a light brush and go slowly to avoid scratching and bending the coil fins.

5.   Rust Resistant Coatings

If you live in a coastal area where the moisture and salt content in the air is high, the risk of rust formation is much higher. It’s a great idea to invest in outdoor units with a rust resistant coating to minimize the risks of corrosion.

6.   Clean the AC Filters

The AC filters should be cleaned every two weeks and a smart AC controller can remind you if you’re forgetful. A clean air filter will boost performance and efficiency and extend the useful lifespan of the equipment too.

7.   Fit a Cover

A waterproof AC unit cover can be placed over the unit when it’s not in use to prevent rust formation caused by excessive air moisture.

8.   Schedule Regular Annual Maintenance

An annual maintenance visit will ensure that your AC system is working at optimal efficiency. During the inspection, the technician may identify potential issues that can develop into larger problems that are more expensive to fix. This includes rust issues and the spread of corrosion that can cause a lot of damage quickly.

In Conclusion

The spread of rust through your AC system can cause a lot of problems, including loss of performance, a lack of sufficient airflow, expensive repair bills, and even a system failure. The best way to avoid these problems is to schedule an annual inspection and tune-up before the start of each cooling season.