Finds Coating Solution
Modified phenols provide protection, flexibility BY JACK SINE
Like many wastewater plants, the Baton Rouge, Lou- isiana, facility has been fighting an ongoing battle with hydrogen sulfide’s effect on its air conditioning
systems. But, because it’s located by the ocean, it also had to
protect against damage from salt in the air.
DANGERS OF H2S AND SALT AIR
Hydrogen sulfide gas (H2S) forms in wastewater collection
systems and can create septic conditions. Collection systems
in warm climates that have a relatively flat grade or do not
have flow-through velocities of two feet per minute or above
create environments conducive to the growth of bacteria.
Septic conditions occur when bacteria use all of the available
oxygen when decomposing the organic material in wastewater. The bacteria reduce sulfur compounds, creating sulfides
that combine with hydrogen atoms to form H2S gas.
This gas has a particularly destructive oxidizing effect on
aluminum in air conditioning coils and copper tubing, making
coating all these surfaces mandatory.
Salt air is similar, causing oxidation on all metal surfaces.
This is why many HVAC contractors recommend coating every metal surface on air conditioning systems.
“What good is it to coat just the coil?” said Jason Wat-
son, an engineer with Watson Mechanical Services, the HVAC
“My primary coating supplier guarantees its coating for 10
years, but what good does that do when the uncoated parts
fail before the warranty is up?” he said.
In municipal settings, because of budget constraints, it is
difficult to get additional expenses approved, so maintenance
managers often agree to just coil and tubing coatings. “But
when we first came on board,” said Watson, “Baton Rouge
wastewater plant had a five-ton Rheems rooftop unit that
was 8 years old and had all metal surfaces protected by AME-TechniCoat phenolic coating.” Eight years later, that system is
still going strong. “To me, that makes a very solid economic
argument for full coating of all metal services, especially considering the H2S and salt air environment,” he added.
WHAT KIND OF COATING?
There are numerous types of post-coats available in the
United States: polyurethane, epoxy, phenolic, epoxy, poly-
No AC coils are too
large for the proprietary phenolic coating