Detecting and Eliminating Causes of Coil Corrosion and Mold/Fungal Growth
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Detecting and Eliminating Causes of Coil Corrosion and Mold/Fungal Growth

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Detecting and Eliminating Causes of Coil Corrosion and all Bio-Growth
“Providing Solutions for a Healthy Indoor Environment”
Quality Air Consultants – EPA Certified
Parts of Blog; by Alan H. Brothers, Ph.D. and Q.A.C. and by Kevin Griffis CIAQ, CIE, EPA Certified in Safe HVAC Environmental Techniques, and the recent Techniques and products for proper maintenance and efficacy, and longevity, of you HVAC and promoting good Indoor Air Quality Controls.
External coil corrosion appears to be on the rise. While the possible causes of coil corrosion can stem from poorly manufactured copper, as the prices of copper went up, the manufactures made the copper tubing thinner and less longevity, chemical residue from coil manufacturing, and other problems that initiate the corrosion process long before the coils arrive on a job-site, the majority of problems occur when environmental acids corrode coils from the outside in.
On the coastal areas which also means 100 -150 miles inward the spoil is full of sulfides, such as hydrogen sulfide, acids, which is corrosive to copper, these elements rise from the ground as gasses and enter the condensation produced by the coils and fins and the water becomes corrosive. Also you have salt in the air, a corrosive, acid rain; everyone has seen the rust and corrosion along coastal areas. This rusting, deterioration, and corrosion is happening in every air handler in the area and by the time we get to look at units it is already in a heavy process along the coils and no service or maintenance has done any prevention for this problem; which by the way is the number “1” effect that causes and will determine the live of a HVAC system.
With the cost of copper rising and the HVAC manufacture’s stretching and thinning of the copper used to save cost, and the fact of no preventatives being applied during maintenance, you HVAC does not have any thing preventing this deterioration inside the air handler. Consumer activist groups have found the expected time before a Freon leak due to corrosion is in the first 5 years; and needing new fins and coils about the same.
These units properly maintained for the environmental issues of the HVAC would last 15-20 years with a micro-shield type sealant that is applied every year to coat all metal, copper, aluminum components of the air handler and it is mold proof and prevents rust as it is a UV Teflon mold-proof, moisture proof coating.
*Remember as the activist groups quickly found out the manufacture’s goal is to sell you a new unit every 7 ½ years.
We recommend to person buying a new unit or building a home to have the units sealed with all the environmental sealants before installation.
There is also a product called a “fin-saver” that attaches to the copper line, outside or near unit as it is one continuous copper line that runs from the outside compressor into the air-handler through the fins and back out to compressor. This device has diodes in it that wrap around the copper pipe and change the molecular structure of the copper that does makes it corrosive and stops the main corrosion from happening. This is a no-fail device as it is not electric or mechanical in anyway, needs no maintenance, just installation.
So with a shield approved by EPA – Safe Environmental HVAC techniques and a fin saver installed, and maintenance once a year with the sealant, you unit could go back to the 20 year longevity it should have.
A case in point is For example, a rooftop unit in a coastal area could be corroded from ocean salt. Household bleaches, aerosol sprays, high humidity, and other prevalent factors found in every home can damage an indoor residential unit coil. An abundance of fertilizers, industrial plant processes, pollution, or acid rain can corrode outdoor condensing coils.
The following list illustrates sources of coil corrosion that could be overlooked by service technicians on commercial HVAC systems:
·         fermenting yeast (lactic acid from milk) in a bakery walk-in cooler
·         chlorine from an indoor swimming pool or aquatic process
·         urine (ammonia) from dead animals in meat processing plant coolers
·         sulfur from well water used in cleaning coils or rooms with coils
·         fertilizer (ammonia) in agricultural building evaporation coolers
Two Types of Environmental Corrosion
The two most common forms of coil corrosion are pitting and formicary. These two corrosive processes can occur in as little as a few weeks after installation. More typically, corrosion will begin appearing within a one-to-four-year period. The ability to distinguish between pitting and formicary corrosion might help detect and eliminate the cause. For example, pitting is typically caused by the presence of chlorides or fluorides. Chlorides are found in numerous items such as snow-melting crystals, toilet bowl/tile cleaners, dishwasher detergents, fabric softeners, vinyl fabrics, carpeting, paint strippers, etc. Fluorides are used in many municipal water treatment plants. Pitting, which appears on the exterior of the copper tube, is usually visible to the naked eye. It is caused by an aggressive attack of an anion, which is a negative-charged chemical species. The anions search for positive-charged species called cations, which are abundant in copper. Pitting will eventually break through to the inside of the tubing and create a leaking condition.
Formicary corrosion is associated with pinholes in the copper tube walls. Although this type of pinhole corrosion is not usually visible to the naked eye, some black or blue-gray deposits often can be seen on the surface. Formicary corrosion also exhibits a subsurface network of microscopic corroded tunnels within the tubing wall that resemble ant nest-type structures, immensely larger than the surface pinholes above them. Formicary corrosion is caused by organic acids such as acetic and formic acids. Acetic acids or the derivative acetate are abundant in numerous household products such as adhesives, paneling, particle board, silicone caulking, cleaning solvents, vinegar, foam insulation, and dozens of other commonly found products in the home or commercial/industrial workplace. Formic acid can be found in cosmetics, disinfectants, tobacco and wood smoke, latex paints, plywood, and dozens of other materials.
Given these common products containing organic acids attack copper, it is not surprising that coil corrosion occurs at alarming rates. The rise in corrosion the last 20 years might also be aggravated by the trend in tighter building construction methods, which allows less outside air induction to dilute or clear away these corrosive, indoor buildups. Even so, both pitting and formicary corrosions need two additional ingredients—oxygen and water. While oxygen is nearly unavoidable, limiting moisture might help the service technician fight or decelerate the problem.
This is a two headed problem as too much condensation inside the air-handler and it sitting in the condensation tray or pan cause corrosion and fungal and bacterial growth. Yes, this does include the toxic molds and air-borne spores that are called “mycotoxins” that are inhaled by the occupant; there are also air borne organisms of bacteria.
So the answer would be; to eliminate the most of the condensation in the unit, get it out as fast as possible when running, and also not let it sit in the trays while unit is off and water is stagnate.  
EPA Safe Environmental Techniques and QAC have a end of the line “Trap pump” which works as your trap in condensation line and keeps the condensation water primed like a water pump.
  •  The trap being installed at the end can let the water line be straight coming out of unit instead of a normal “U” shaped trap right outside unit (within a foot of unit); which is the major cause of stoppage and clogged lines that causes flooding of the HVAC. Your trap pump works the same except at the end of line in which is does not allow the sludge and bacteria/fungal build-up to be large enough to block and get caught in trap right outside unit. By the time debris runs all the way through line it is broken up and dissolved and will not clog the pump.
  •  The pump captures the negative air flow that helps push the water out of unit and keep it primed so more than 30% more water is expelled while unit is running.* In mid-summer time a 3 ton unit will produce 7-9 pounds of water per hour!
  • The pump has a seal in it that when the unit shuts off; cycles as we call it, the pump will seal the line and hold the water in line, even in a 4-5 hundred foot long line; otherwise in a normal line with just an open end, the water is pulled back up line and into unit and sits until the unit cycles on again. So the pump promises the water is primed and held in line the moment the unit cycles, and no water will recede into the unit and fill trays with stagnate water.
  • Also with a normal open end line outside, the unit then cycles on and we have timed it taking up to 45 minutes before the first drops of water come out of condensation line. It has to prime itself every time it cycles. This is eliminated by the pump which you can at anytime go out and take the top off and lift the seal, and see the “tap clean” water sitting in the pump, ready to go.
  • This is also a “no-fail” component; no electricity, no mechanical.
In summary, you are stopping chances of a clogged trap and flooding, you are keeping the water out of unit that grows mold and bacteria, you are expelling 30 % more water out of unit, and also holding the water in the line ready primed to immediately start coming out of line when unit cycles on; instead of having to prime itself. Maintenance would be taking top off and cleaning once a year as to grass clippings, debris from yard, shrubs, and weeds, etc.
In our now “Go-Green world” we have put the water you are manufacturing in your unit to work, as having the pump in a flower garden or herb area to water them during day, as the pump sometime can get going so fast it is like a small sprinkler.
And no forgetting stopping corrosion as water is not again sitting in unit and puddling in bottom of casing, or insulation siding on the doors or floor of the unit inside and being blown around by the blower fan.
Galvanic Corrosion
When two dissimilar metals, such as copper tubing and aluminum fins, are in contact with each other, a "galvanic couple" is formed, and the phenomenon of galvanic corrosion occurs. In this galvanic couple, the metal that corrodes and the metal that is protected depend on their relative positions in the galvanic series. Moisture is again a key factor in this corrosive process because it acts as the electrolyte needed in the reaction. Sea water accelerates the galvanic reaction because of its higher conductivity than fresh water and because salts can destroy the protective barriers on metal surfaces. The potential for galvanic corrosion is always present between two dissimilar metals. But how quickly galvanic corrosion results in system damage depends on variables like the electrolyte conductivity, the amount of oxygen present and relative surface areas of each metal. The preventatives and fin savers prevent this corrosion from taking place; it does not let the water reach the metal surfaces or copper surfaces as it is coated with the UV Teflon microbial sealant.
Keeping Coils Clean to Fight Corrosion and Fungal /Bacteria Growth
Outdoor condensing coils can best fight corrosion with periodic cleaning. Water is suitable, but existing corrosion and buildup typically are removed more completely with a coil cleaner. Numerous Eco-Friendly acid-based and alkaline-based coil cleaners are available. However, proper rinsing is important to avoid the coil cleaner chemical residue that could initiate the corrosion process. Some alkaline cleaners tout the fact that they are "non-acid" to capitalize on the belief that acids cause corrosion. However, alkaline cleaners also need to be rinsed thoroughly just like acid-based cleaners because alkaline residues can also corrode aluminum and other materials.
Outdoor coils located in areas where corrosives are prevalent, such as heavy industrial areas with acid rain or coastal areas where ocean salt is a factor, should have frequently scheduled, periodic cleanings.
Corrosion from the Manufacturing Process
While no available statistics reveal the extent of environmental corrosion, it may cause the majority of coil corrosion problems. However, the manufacturing process itself can also initiate coil corrosion prior to installation. Manufacturing problems can be related to anything from poorly constructed copper tubing or lubricants coil manufactures use at their plants.
Replacing coils corroded during the manufacturing process or using substandard copper may not alleviate corrosion because the problem may be inherent in the product. This is where environmental investigation comes in and it is determined the best action to take, and a protocol set for the maintenance of the particular unit.
Coatings to Protect Coils from Corrosion
Protective coatings are an option for new coils that are destined for corrosive applications and for existing coils that have been repeatedly replaced due to corrosion. Numerous coatings exist. However, most coil coatings are composed of either silanes or polymers, but the best is a Teflon microbial coating. The advantage of coatings is they make coils virtually corrosion-proof when properly applied and maintained. Reducing corrosion can improve long-term performance and reduce replacement costs. New coils with coatings can be oversized to offset the heat transfer loss. Some coating manufacturers actually claim an increase in heat transfer, due to the way in which water condenses and drips off coated coils.
For existing coils, some coatings can be applied in the field by QAC specialists who clean and then spray a coating on the coil. Other coatings can be applied by service technicians in the field. Whether a field application is possible depends mostly on the depth of the coil. Other coatings require sending the coil to the coating manufacturer or a specially-trained applicator. Probably the most difficult area to reach with a coating is the gap between the fin and tube. There are two common types of coil coatings, and both differ greatly in chemical make-up and performance: the best time to do this is when a new unit is going to be installed, as the ducts, plenums, and the air-handler can be sealed.
When preparing to make a service call concerning a corroded coil, identify the type of corrosion then search for environmental cause(s). If possible, eliminate the source of corrosion. For irretrievable sources, coatings might be the only answer. Call an Environmentally trained HVAC technician that is Certified in both the regular HVAC operations and the environmental side of the HVAC as well.
Just recently the IAQA (Indoor Air Quality Assoc.) and ASHRAE the HVAC technicians lead organization and oversee of HVAC procedures have joined forces to enlighten the HVAC tech to the Environmental side of the main culprit of poor Indoor Air Quality, Sick Building Syndrome, and the health and illness’ that can be inhaled by occupants or employees as they inhale the “conditioned air” in a home or building. The understanding and awareness has taken place to understand the importance and severity of toxins being inhaled and ingested by persons when an HVAC system has not been maintained by environmentally trained technicians.
All chemicals used in Remediation or Maintenance of HVAC EPA approved and CDC Safe Eco-Friendly Products.
Bio:Dr. Alan H. Brothers is a senior materials engineer for Mainstream Engineering, Rockledge, Fla., a leading research & development company specializing in thermal control and heat pump development. Brothers has a Bachelor's Degree in Engineering and Applied Science from California Institute of Technology, and a doctorate in Materials Science and Engineering from Northwestern University. Brothers continued his doctoral research on the processing and properties of light metals under a Helmholtz Fellowship from the Hahn-Meitner Institute in Berlin. Additionally he has researched the corrosion of aluminum in organic liquids and the use of coatings to mitigate corrosion in aluminum and galvanized steel HVAC components. He is the author or co-author of twelve peer-reviewed technical publications and a number of conference presentations
Q.A.C. – Quality Air Consultants is the oldest and original environmental company is the south GA. area for the consulting, assessments, and Remediation and Maintaining of HVAC systems for a Quality Indoor Air in Commercial or Residential Settings Offers maintenance Contracts for companies and residential HVAC systems to ensure healthy and safe air Indoors. Testing and Analysis is available also.
Sick Building Syndrome is when a company or office building has contaminated and poor Indoor Air quality, and complaints from employees.
Studies have been done to prove when these type companies HVAC systems and indoor air is environmentally maintained by Certified Company that absenteeism goes down rapidly, Production goes up dramatically, and the overall well-being of workforce has better work habits, attitudes improve, and office employee energy is improved.

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