Forget Coated and Sorta-Stainless Steel. FRP and Composites are Functionally Corrosion Immune
Composite construction is significantly more corrosion resistant than even 316 stainless steel construction at a cost competitive with 304 stainless steel.
How much better corrosion resistance?
Since the 1950s when the use of fiber reinforced polymers began in marine construction, not a single instance of composite corrosion has ever been recorded. Mechanical components such as fans and ductwork fabricated from Fiber-reinforced-polymers have been in service for decades, and have established an industry-wide reputation for corrosion resistance.
C.A.D. can provide air handling systems using an ultra-modern resin-infused fiberglass technology that is factory guaranteed against corrosion for life.
H.V.A.C equipment is frequently specified to be painted; often not for aesthetic reasons but to protect the painted substrate from corrosion caused by exposure to harsh environments. Consulting engineers concerned about the long-term longevity of paint systems often specify testing based on ASTM B-117 Standard Practice for operating salt spray (fog) apparatus, with requirements usually ranging from 500 to 4,000 hours.
ASTM B-117 Salt Spray Test Comparison @ 4,000 hrs.
The K-Kore™ panel in this photo only shows signs of salt buildup in the scribe. The panel looks identical after 5,000 and 8,000 hours, and no corrosion is expected even after 25 years (200,000+ hours) of exposure to a saline environment. Note that the Epoxy Control system is rated for 4,000 hours salt-spray and its performance is considered passable. The scribe simulates the effect of a scratch or dent that may happen during installation.
And, since the corrosion resistance is an inherent property of the material itself rather than a surface coating like paint, anodization, or galvanization, the pigmented composite material used in the construction of C.A.D. equipment will never delaminate or fail even if deeply scratched.
Compare this to the performance of 304 stainless in coastal environments, where it’s not unheard of for this material -- and equipment manufactured from it -- to become severely corroded in as little as two to three years.
Galvanic corrosion is also another issue that metal units experience. This will often occur when fasteners are not the same metal type as the air handling unit base metal. Galvanic corrosion can be seen on the exterior of air handling units, in cooling coil sections as well as humidifier sections where the presence of water is the link needed to make galvanic corrosion happen. The effects are much less with freshwater as opposed to saltwater. This will be more prevalent in coastal areas making Composite Air Design a better choice.