April 23, 2020
An important consideration in many HVAC applications is corrosion resistance of the unit’s paneling. “Corrosion alone accounts for approximately 40% of all equipment failures in industrial facilities,” according to Continuing Education and Development (CED) Engineering. Premature corrosion of HVAC units can be a serious problem leading to expensive repairs or entire system replacement. CED experts say, “facilities located in potentially corrosive outdoor environments such as seacoast, industrial sites, heavily populated urban areas, some rural locations, or combinations are exposed to various threats of salt laden corrosive elements, various air borne molecular contaminants, and water vapor.” Environmental contaminants often create electrolytes that facilitate the corrosion process, especially when combined with other factors like wind direction, humidity, water, fog, temperature, proximity to pollutant source, and dust or particle contamination. This is especially true for rooftop and air handler units which are exposed to extreme weather conditions that can accelerate the corrosion process.
So how do you know if your HVAC equipment is built to withstand the elements? When designing new products, engineers at Daikin don’t take these risks lightly. To combat the problem, Daikin exterior paneling employs pre-galvanized steel that is treated with a base primer and high-quality polyester resin topcoat to resist natural corrosion processes. This allows our products to provide a lifetime of effective service while maintaining an aesthetically sound exterior. To prove its effectiveness, Daikin recently submitted its panels to multiple types of corrosion resistance testing, conducted by several third-party testing facilities.
Testing Standards ASTM B117 (Salt Spray) and ASTM D1654 (Corrosion Testing and Evaluation) were both employed to test and rate corrosion resistance of Daikin packaged rooftops and air handlers. Daikin had panels subjected to 3,000 hours of salt spray exposure per B117, and scribed panels subjected to 1,000 hours of salt spray per D1654.
In the industry standard test – subjecting unaltered panels to an ASTM B117 salt spray environment – Daikin panels could withstand a minimum of 3,000 hours exposure without showing any visible rust. Check out the before and after photos below:
In the more rigorous ASTM D1654 Corrosion Testing and Evaluation, Daikin tested both scribed and unscribed panels, subjecting them to 1,000 hours of ASTM B117-specified salt spray. Unit A1, shown in figure 3 below, shows one sample scribed with an “X” to alter the panel per ASTM D1654. Scribing deliberately removes paint and damages other layers of protection. This is not the normal condition of equipment, but rather a way to test the longevity of the paint in a worst-case condition. There is little question that a corrosive environment will degrade the scribed line itself. Instead, the relevant measure of corrosion resistance is how adjacent, undamaged surfaces resist corrosive elements creeping into them from the exposed surface of the scribed line. Figure 3 shows the state of corrosion before the blisters were scraped off. Unit B1 (figure 4), on the other hand, shows an example of an unaltered sample, which was used to compare results according to different amounts of exterior damage. All ratings are on a formal scale of 0 to 10, with 10 being the most corrosion-resistant. Daikin’s pass-fail criteria is a 9 or 10 rating with no rust. Using ASTM D1654’s quantitative results, all panels achieved 10 out of 10 on rust and corrosion creepage, and 9 out of 10 on blister evaluation. The results of this test are shown in the images below.
To ensure your units are performing as intended, corrosion control is an essential part of HVAC design. Both tests described above put Daikin’s corrosion-resistance well ahead of industry standards, with a quality few competitors can match. That’s because at Daikin we see corrosion control as a key factor in enhancing energy efficiency, productivity, and equipment life. Get in touch with your local Daikin Sales Rep to learn more about corrosion control in our product offerings.