SELECTION GUIDE:ENVIRONMENTAL CORROSIONPROTECTION

COMMERCIAL PRODUCTS:CONDENSER COILS AND COOLING/HEATING COILS

MICROCHANNEL ALUMINUM ALLOY HEAT EXCHANGERALUMINUM-FIN/COPPER-TUBE COILSCOPPER-FIN/COPPER-TUBE COILSPRE-COATED ALUMINUM-FIN/COPPER-TUBE COILSE-COATED ALUMINUM-FIN/COPPER-TUBE COILSE-COATED COPPER-FIN/COPPER-TUBE COILS

Carrier CorporationSyracuse, New York

April 2006

INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

WHAT CAUSES CORROSION? . . . . . . . . . . . . . . . 4Galvanic Corrosion . . . . . . . . . . . . . . . . . . . . . . . . . 4General Corrosion . . . . . . . . . . . . . . . . . . . . . . . . . 5

IDENTIFICATION OF POTENTIALLYCORROSIVE ENVIRONMENTS . . . . . . . . . . . . . . 6

Coastal / Marine . . . . . . . . . . . . . . . . . . . . . . . . . . . 6Industrial . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6Combination Marine / Industrial . . . . . . . . . . . . . . 7Urban . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7Rural . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7Localized Environment-Corrosivityof the Surroundings . . . . . . . . . . . . . . . . . . . . . . . . 7

INSTALLATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

CORROSION PROTECTION OPTIONS . . . . . . . . 9Condenser Coils . . . . . . . . . . . . . . . . . . . . . . . . . . . 9Cooling / Heating Coils . . . . . . . . . . . . . . . . . . . . 12

Field-Applied Coatings . . . . . . . . . . . . . . . . . . . . 13E-Coated Material and Chemical Resistance . . . . 13

SELECTION SUMMARY TABLES . . . . . . . . . . . 15Protection Option Selection . . . . . . . . . . . . . . . . . 15

COIL MAINTENANCE AND CLEANING RECOMMENDATIONS . . . . . . . . . . 19

RELIABILITY TESTING / QUALITY ASSURANCE AT CARRIER . . . . . . . . 19

Kesternich Testing . . . . . . . . . . . . . . . . . . . . . . . . 19Steam Tests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19Salt Spray Tests . . . . . . . . . . . . . . . . . . . . . . . . . . 19Kure Beach Studies . . . . . . . . . . . . . . . . . . . . . . . 19Cyclic Corrosion Testing . . . . . . . . . . . . . . . . . . . 19Prohesion™ Cycle Test Results Comparison . . . . 19Carrier Marine One Testing . . . . . . . . . . . . . . . . . 20

APPENDIX . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21E-Coating Chemical Resistance Guide . . . . . . . . 21

TABLE OF CONTENTS

INTRODUCTION

Corrosion is costly. By definition, corrosion is thedestruction or deterioration of a metal or alloythrough chemical, physical or electrochemical reaction with the environment. In HVAC equipment,exposure to various elements in the environmentcan lead to localized and/or general corrosion ofcondenser coils or heating and cooling coils. Theuse of improperly protected coils in corrosive locations may lead to premature performance degradation, unsightly surface conditions and, underthe most severe conditions, equipment failure.These effects may be costly to the customer andmay result in lost sales caused by the perception ofpoor product quality. Fortunately, with proper coilselection, corrosion can in most cases be minimized.

The following types of commercial equipment maybe susceptible to corrosion:

• Rooftop Units• Air-Cooled Chillers• Air-Cooled Condensing Units• Remote Air-Cooled Condensers with

Make-Up Air-Handling Equipment

If these units are improperly applied or left unpro-tected, they can experience rapid corrosion fromexposure to aggressive elements. However, measurescan be taken to identify potentially corrosive environments prior to equipment selection.

This guide will assist in the selection of appropriatecoils and long-term product solutions in potentiallycorrosive environments by describing:

• What causes corrosion• How to identify potentially harmful

environments• How to select proper coil protection

With this information, intelligent equipment selection decisions can be made to optimize thelevel of corrosion protection and maintain the highest level of long-term equipment quality.

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WHAT CAUSES CORROSION?

There are many types of corrosion. The two formsof corrosion most common to HVAC equipment areknown as galvanic and general corrosion. Each ofthese corrosion types can lead to equipment failure.

Galvanic Corrosion

When dissimilar metals are in contact in the presence of an electrolyte, a reaction occurs. Thisreaction is known as galvanic corrosion. For galvanic corrosion to occur, there must be a metalliccouple between two or more dissimilar metals in thepresence of an electrolyte. If any one of the factorsis not present, galvanic corrosion will not occur.

Galvanic corrosion of copper tube/aluminum finheat exchanger coils results in fin degradation,which may ultimately lead to the destruction of thecoil. Galvanic corrosion of the unprotected coilbegins at the bi-metallic couple between the coppertube and aluminum fin. Because the aluminum isless noble than copper, the aluminum material corrodes. Figure 1 shows a typical standard coilprior to attack from galvanic corrosion.

As galvanic corrosion begins in the standard coilconstruction, the aluminum fin deteriorates startingat the copper/aluminum interface (Figure 2).Corrosion of the aluminum fin continues until coilperformance is adversely affected because of theoxide build-up at the copper tube/aluminum fininterface, which creates thermal resistance. Anotherresult of corrosion is severe visual deterioration,including aluminum oxide build-up around the tubesurface and within the fin pack, flaking aluminumfins, fins falling from the coil surface in thin sheetsand total removal of the aluminum fin material.

Fig. 1. Standard coil construction.

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Fig. 2. Galvanic corrosion begins.

Bi-Metallic Construction

The standard coil is manufactured from coppertubes mechanically bonded to aluminum fins. Thisbond creates a classic bi-metallic couple necessaryfor galvanic corrosion. An electrolyte in the presence of the copper-tube and aluminum-fin couple is sufficient to initiate a corrosion reaction.However, elimination of the bi-metallic couple caneliminate galvanic corrosion. This can be accomplished with an all-copper coil, which eliminates the presence of dissimilar metals, one ofthe requirements for galvanic corrosion. Anotherway to prevent galvanic corrosion is by isolation ofthe two metals through a protective coating. Theprotective coating will create a barrier between themetallic couple and the electrolyte, thereby eliminating the electrolyte, one of the requirementsfor galvanic corrosion. A third way to prevent galvanic corrosion is to insulate the copper from thealuminum through the use of a pre-coated aluminumfin. The insulation eliminates the electrical contactof the dissimilar metals, one of the requirements forgalvanic corrosion.

Galvanic corrosion can also be decreased throughmaterial selection. The microchannel heat exchanger (MCHX) is an example of a coil designthat utilizes galvanic corrosion to help protect theintegrity of the aluminum alloy design. Through useof a less noble (and therefore less resistant to corrosion) coating on the tube surface, the tube, finand braze material are specifically made cathodicwith respect to the coating, thus enabling the coatingto preferentially corrode, protecting the main elements of the heat exchanger.

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The Electrolyte

Electrolytes are substances that are electrically conductive when in solution. Common electrolytesmay include chloride contaminants from sourcessuch as seawater, road salts, pool cleaners, laundryfacilities and household cleaning agents. These electrolytes are typically sodium or calcium chloride-based compounds. Other relevant contam-inants that may be present include sulfur and nitrogen compounds from the combustion of coaland fuel oils.

The most common sources of chloride-based contamination are marine and coastal environments.Sea spray, mist, and fog contain tiny droplets of saltwater that can be transported more than severalmiles by ocean breezes and tidal currents. It is notuncommon to experience salt-water contaminationmany miles from the coast. As a result, protectionfrom ocean-borne electrolytes in inland areas maybe necessary.

General Corrosion

General corrosion is the degradation of metal causedby a reaction with the environment, such as oxidationand chemical attack of the metallic surface. Sincegeneral corrosion consumes metal and forms metaloxides, unsightly surface conditions result. Forexample, copper is susceptible to attack from sulfurcontaining gases. The result is the formation of anon-protective layer on the material surface. Thecopper fins will often become very brittle, with thecorrosion product being non-adherent to the coppermetal surface. Unprotected metal will continue toreact with the contaminant and corrode. Undersevere, prolonged conditions, the metal continues tocorrode until the integrity of the equipment is jeopardized. Unprotected copper in polluted industrialenvironments can lead to failure of the refrigerationsystem. Sulfur and nitrogen based electrolytes incombination with chloride environments are oftenthe cause of accelerated corrosion of copper.

Failure of a contaminated copper-fin coil can resultfrom fin degradation and ultimate loss of tubeintegrity. Furthermore, surface tarnish on copper,evident as black, red, green, brown or yellowdeposits, leads to the perception of poor quality.

Fig. 3. Clean copper tube.

Fig. 4. Oxidation begins.

Fig. 5. Tube failure.

General corrosion of copper due to a contaminatedenvironment is illustrated as follows. A clean coppertube in an uncontaminated atmosphere maintainssystem integrity (Figure 3). However, in a contami-nated atmosphere, metal oxides begin to form on thecopper tube (Figure 4). Prolonged exposure to acontaminated atmosphere results in tube failure(Figure 5).

IDENTIFICATION OF POTENTIALLYCORROSIVE ENVIRONMENTS

A corrosive environment must be clearly identifiedand understood before proper coil protection can beselected. In addition, the identification of a corrosiveenvironment is important so that indoor air qualitycodes and generally accepted practices may beaddressed, since corrosive environments may have adetrimental effect on indoor air quality.

Potentially corrosive outdoor environments includeareas adjacent to the seacoast, industrial sites, heavily populated urban areas, some rural locations,or combinations of any of these environments. Inair-handling applications, some indoor environmentssuch as swimming pool areas, water treatment facil-ities, and industrial process areas can produce corro-sive atmospheres.

Local environments must also be considered; closeproximity to laundry facilities, diesel-burningdevices/exhaust piping, sewer vents, traffic, etc. canalso lead to premature failure of improperly selectedequipment.

Coastal / Marine

Many emerging HVAC marketshave a majority of their popula-tions located in coastal areas.This leads to an increased numberof air conditioning applicationslocated in corrosive environments.

Coastal or marine environments are characterized by the abundance of sodium chloride (salt) that iscarried by sea spray, mist or fog. Most importantlythis salt contamination can be carried many milesinland from the coast. Even if the HVAC equipmentis a substantial distance from the ocean, corrosionfrom salt contamination can still occur if the equipment is not properly protected.

Distance from the ocean, prevailing wind direction,relative humidity, wet/dry time and coil temperaturewill determine the severity of corrosion in the

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coastal environment. As a result, the followingshould be considered when the potential for coastalcontamination exists:

• Is the unit near the ocean? Visit the proposedinstallation site. How far away from the ocean is thesite? Are the prevailing winds from the ocean? If so,the potential for severe coastal corrosion should beexpected and appropriate protection is required.

• Is there corrosion on exterior structures, otherHVAC equipment, or other equipment? Look aroundthe installation site and surrounding areas. If there isevidence of corrosion, chances are high that corrosive contaminants exist and suitable protectionis required.

Industrial

Industrial applications areassociated with a host ofdiverse conditions with thepotential to produce variouscorrosive emissions. Sulfurand nitrogen containing con-taminants are most oftenlinked but not limited toindustrial and high-density urban environments.Combustion of coal and fuel oils release sulfuroxides (SO2, SO3) and nitrogen oxides (NOx) into the atmosphere. These gases accumulate in theatmosphere and return to the ground in the form ofacid rain or low pH dew.

Not only are industrial emissions potentially corrosive, many industrial dust particles can beladen with harmful metal oxides, chlorides, sulfates,sulfuric acid, carbon and carbon compounds. Theseparticles, in the presence of oxygen, water or highhumidity environments can be highly corrosive.

Note: These particles/contaminants can be carriedfor many miles.

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Combination Marine/Industrial

Salt-laden seawater mist,combined with the harmfulemissions of an industrialenvironment, poses a severethreat to the life of HVACequipment. The combinedeffects of salt mist andindustrial emissions willaccelerate corrosion. Thisenvironment requires superior corrosion resistantproperties for air-conditioning components to maintain some level of product quality. Completeencapsulation of the coil surfaces is recommended.E-Coated copper-fin coils should be considered.

Urban

Highly populated areas generally have high levels ofautomobile emissions andincreased rates of buildingheating fuel combustion.Both conditions elevate sulfur oxide (SOx) and nitrogen oxide (NOx) concentrations. Corrosionseverity in this environment is a function of the pollution levels which in turn depend on several factors including population density for the area,emission control and pollution standards.

Any HVAC equipment installed near to dieselexhaust, incinerator discharge stacks, fuel burningboiler stacks, areas exposed to fossil fuel combustion emissions, or areas with high automobile emissions should be considered anindustrial application. E-Coated aluminum-fin coils would be the only acceptable protection inthese environments.

Rural

A rural environment typically is unpolluted byexhaust and sulfur containing gasses. Typically arural environment is sufficiently inland that contam-ination and high humidity from coastal waters arenot present. Protection in these environments is

typically not required beyond the standardaluminum fin/copper tube coil construction or themicrochannel heat exchanger.

Sometimes, however, rural environments containhigh levels of ammonia and nitrogen contaminationfrom animal excrement, fertilizers, and high concentrations of diesel exhaust. These environmentsshould be handled much like industrial applicationswith E-Coated coil protection.

Localized Environment - Corrosivity of the Surroundings

All of the above environments are subject to“Micro-Climates” which can significantly increasethe corrosivity of the environment. Care should betaken to ensure that the localized environment surrounding the HVAC equipment does not containcontaminants that will be detrimental to the coil. Anexample would be equipment placed near a dieselloading area. Although the general area in which thebuilding is located may meet the scope of a coastalor marine environment, the localized elements thatsurround the equipment may actually classify theapplication as industrial, and protection of the coilshould be planned accordingly.

Situations to consider when determining the level ofcorrosivity of the localized environment:

Proximity to:• Sea water• Automobile traffic• Bus traffic• Truck traffic• Power plants• Factories• Breweries and food processing plants• Wastewater treatment plants• Dumps and incineration plants• Cruise ships and shipping traffic• Swampy areas (rotting vegetation)

Contributing factors such as:• Prevailing wind direction• Acid rain (sources may be hundreds of miles away)• Humidity levels• Duration of wetness• Condensation

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INSTALLATION

The following situations also contribute to the levelof corrosivity of the localized environment:

• Laundry vents or exhausts• Dryer exhausts• Laundry rooms• Exhaust vents

• Diesel tank locations• Diesel loading areas• Diesel boiler rooms/exhausts• Proximity to cooling towers where

carry-over is possible

• Proximity to sprinkler systems (where over-spray is possible)

• Kitchen exhaust vents• Sewer exhaust vents• Areas where insecticide will be utilized• Areas where fertilizers are applied• Pools/hot tubs• Chemical/cleaner storage areas• Loading docks• Bus loading areas

CORROSION PROTECTION OPTIONS

The highest level of product quality can be assuredwhen the right coil option is applied. The choicesavailable on Carrier’s commercial products offerprotection for many aggressive environments.

Condenser Coils

Standard Coil Construction

The standard condenser coil has copper-tubesmechanically bonded to aluminum-fins with wavyenhancements. Figure 6 shows a cross-section of acopper tube and several aluminum fins. High thermal efficiency is achieved through direct metallic contact between the tube and fin. As aresult, maximum thermal performance is achievedwith this high efficiency coil design provided thereis no corrosion.

Fig. 6. Standard coil construction.

The standard coil generally provides high performance for non-corrosive environments (e.g.,non-polluted rural environments). Application of thiscoil in any environment containing corrosive consti-tuents is not recommended because of the likelihoodof visible deterioration resulting from corrosion.

Pre-Coated Aluminum-Fin Coils

Pre-coated aluminum-fin coils have a durable epoxy coating applied to the fin. This design offers protection in mildly corrosive coastal environments,but is not recommended in severe industrial orsevere coastal environments.

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Aluminum fin stock is coated with a baked-onepoxy coating prior to the fin stamping process(Figure 7). Coating of the fin material prior to the finstamping process is known as “pre-coating.” Thepre-coated fin material is then stamped to form awavy fin pattern for optimum thermal performance.The wavy design can be recognized by thevertical corrugation on the fin face. Vertical corru-gations increase the fin’s effective surface area andfurther enhance heat transfer properties.

A thin layer of inert epoxy pre-coating materialinsulates the dissimilar metals of the coil from oneanother. As a result, the electrical connectionbetween the copper and aluminum is broken, thuspreventing galvanic corrosion. In mild coastal envi-ronments pre-coated coils are an economical alternative to E-Coated coils and offer substantialcorrosion protection beyond the standard uncoatedcopper tube/aluminum fin coil.

Microchannel Coil

In contrast to standard condenser coils, microchannelcondenser coils are constructed utilizing an all-aluminum brazed fin construction. A microchannelcoil is composed of three key components: the flat microchannel tube, the fins located betweenalternating layers of microchannel tubes, and tworefrigerant manifolds. The manifolds, microchanneltubes, and fins are joined together into a single coilusing a nitrogen-charged brazing furnace. Overallproduct quality and integrity are maximized sinceonly one uniform braze in the furnace is required ascompared to 200 or 300 manually brazed connectionson traditional copper/aluminum coils.

Fig. 7. Pre-coated coil assembly.

The refrigerant carrying tube is essentially flat, withits interior sectioned into a series of multiple, parallelflow, microchannels that contain the refrigerant (see Figure 8). In between the flat tube micro-channels are fins that have been optimized toincrease heat transfer.

The flat tube microchannels are layered in parallelwith the tubes connected between two refrigerantdistribution manifolds. The coil is divided into twopasses. One pass is used to de-superheat and condense discharge gas. The second and final passis used to finish condensing and provide liquid subcooling (See Figure 9).

The microchannel heat exchangers are constructedfrom several aluminum alloys in combination withmetallic coatings. The aluminum tube alloy material is initially protected by a metallic layerspecifically chosen to be less noble than the tubematerial, fin and braze material, resulting in any

Fig. 8. Microchannel/fin center.

initial corrosion occurring on this sacrificial layer.Furthermore, the coil has been designed so that anygalvanic couples within the coil are carefully chosento provide the maximum life possible for the coil.

Use of the MCHX will provide the highest performance and a substantial improvement beyondthe standard copper tube/aluminum fin coil for non-corrosive environments, such as non-polluted ruralenvironments. In addition, MCHX coil offers amore economical alternative to pre-coated coils inmild coastal environments. Furthermore, theimproved performance offered by the MCHX coilwill provide increased efficiency and allow for theutilization of an overall smaller coil size. Theseadvantages, along with the other benefits providedby the MCHX coil (including lighter weight, lowerrefrigerant volume, structural rigidity and easycleaning), make the MCHX a logical replacementfor the standard copper tube/aluminum fin condensercoil in non-corrosive environments and an alternative to the pre-coated aluminum fin coil inmild coastal environments. Application of theMCHX coil in severe coastal, industrial or industrialmarine environments is not currently recommended.

Copper-Fin Coils

Copper-fin coils eliminate the bi-metallic bondfound on standard fin coils (Figure 10). A copperwavy fin pattern, void of louvered enhancements, ismechanically bonded to the standard copper tube.All-copper tube sheets are also provided to enhancethe natural resistance of all-copper construction.A protective Mylar strip installed between the coilassembly and sheet metal coil support pan furtherprotects the coil from galvanic corrosion.

Copper-fin coils are priced higher than aluminumpre-coated fin coils, since material costs for copperare greater than aluminum. However, coastal corrosion durability in an unpolluted marine environment can be substantially improved over thestandard or pre-coated coil construction, since thebi-metallic construction is not present.

Fig. 9. Microchannel coil construction.

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TUBES

FINS

MICROCHANNELS

MANIFOLD

FIRST PASS

REFRIGERANT IN

REFRIGERANT OUT

MANIFOLD

SECOND PASS

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Copper-fin coils provide increased corrosion resistance in coastal environments where pollutionsources are not present. Copper is generally resistantto unpolluted coastal environments, since a naturalprotective film is formed to passivate the coppersurfaces. Furthermore, a mono-metal bond existsbetween the tube and the fin. However, uncoatedcopper coils are not suitable for polluted coastalapplications or industrial applications, since manypollutants attack copper. The use of uncoated copperin these applications is not appropriate and must be avoided to ensure long coil life. E-Coated aluminum-fin coils should be considered for such applications.

E-Coated Aluminum-Fin Coils

E-Coated coils provide superior protection againstmany corrosive atmospheres with the exception offormic acid and nitric acid environments. For a complete listing of the chemicals to which the E-Coat is resistant, please refer to the appendix.

E-Coated aluminum-fin coils have an extremelydurable and flexible epoxy coating uniformlyapplied over all coil surfaces for complete encapsu-lation from exposure to the contaminated environment.A consistent coating is achieved through a preciselycontrolled electrocoating process that bonds a thinimpermeable epoxy coating on the specially preparedcoil surfaces.

Electrocoating is a multi-step process that ensuresultra clean coils are properly coated, cured and protected from environmental attack (Figure 11).This process includes complete immersion degreasing to remove contamination and ensure all

Fig. 10. Copper-fin coil assembly.

surfaces are ultra clean. The water bath rinses resid-ual dust and contamination away in preparation forthe E-Coating process. The fundamental principle ofelectrocoating is that the materials with oppositeelectrical charges attract each other. An electrocoatingsystem applies a DC charge to the coil immersed ina bath of oppositely charged epoxy molecules. Themolecules are drawn to the metal, forming an even,continuous film over the entire surface. At a certainpoint, the coating film insulates the metal, stoppingthe attraction, and preventing further coating depo-sition (self-limiting nature of the coating process).

The final rinse bath removes and recovers residualcoating material to ensure a smooth coating andminimizes process waste. A precisely controlledoven bake cures the coating uniformly to ensureconsistent adhesion on all coil surfaces. Finally, aUV protective topcoat is applied to shield the finishfrom ultraviolet degradation and to ensure coatingdurability and long life.

This creates a smooth, consistent and flexible coating that penetrates deep into all coil cavities andcovers the entire coil assembly including the finedges (Figure 12). The process in conjunction withthe coating material results in a less brittle, moreresilient and more durable coating without bridgingbetween adjacent fins than previous phenolic coatings. E-Coated coils provide superior protectionin the most severe environments.

Degreasing

Water Rinse

E-Coat

Final Rinse

Oven Bake

UV Topcoat

Fig. 11. E-Coat process.

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Fig. 13. E-Coated copper/copper coil.

Flexible, consistentand durable epoxycoating. Fills all coilcavities and coversfin surface andedges.

Aluminum Fin

Copper Tube

Cooling/Heating Coils

Standard Coil Construction

The standard cooling/heating coil (water, steam orDirect Expansion) has copper-tubes mechanicallybonded to non-lanced aluminum-fins with a wavypattern embossed on the fin face. The fin pack isassembled with galvanized steel tubesheets and coilcase. This assembly has classic galvanic corrosioncomponents with multi-metal bonds between thefin-and-tube and tube-and-tubesheet.

In cooling applications, condensate accumulates onthe coil surfaces when dehumidification occurs. Wetcoil surfaces resulting from condensation in thepresence of a contaminated airstream will lead togalvanic corrosion if not properly protected.

Potentially corrosive airstreams may not be suitablefor building occupants. If a contaminated airstreamcan lead to corrosion, special consideration withrespect to indoor air quality and potentially harmfulside effects to building occupants is recommended.

Copper-Fin Copper-Tube Coils

Much like the all-copper condenser coil, all-coppercooling/heating coils eliminate the bi-metallic bondfound on standard coils. A copper fin with wavy pattern is mechanically bonded to the standard copper tube to ensure a single-metal assembly. Mostair-handling equipment is available with stainlesssteel tubesheets and coil cases to improve the corrosion durability of the entire coil assembly. As aresult, the potential for corrosion is reduced since bi-metallic couples can be reduced within the coil assembly.

E-Coated Coils

E-Coated coils have the same E-Coating as the condenser coils (see Condenser Coils section onpage 9). All E-Coated coils have a durable and flexible epoxy coating uniformly applied over allcoil surfaces, including tubesheets and coil cases.The coating provides a barrier between the coil surfaces and the corrosive effects of the atmosphereto prevent contamination of the coil surfaces. Since cooling/ heating coils are not exposed to thepotentially harmful ultraviolet rays from the sun, theUV topcoat is unnecessary.

E-Coated Copper-Fin Coils

E-Coated copper-fin coils have the same durableand flexible epoxy coating uniformly applied overall coil surfaces as the E-Coated aluminum-fin coils(Figure 13). However, these coils combine the naturalresistance of all copper construction with completeencapsulation from the E-Coat process. E-Coatedcopper-fin coils should be specified for environmentswith harsh coastal conditions.

Fig. 12. Magnification of E-Coated aluminum-fin copper-tube coil.

Fin Spacing

(FPI) Aluminum-Fin Copper-Fin E-Coated Coil

8 650 500 500

11 650 425 425

14 575 375 375

FPI - Fins per Inch FPM - Feet per Minute

In considering E-Coated coils, it is important to alsoconsider the effects of moisture carryover. Moisturecarryover occurs when accumulated condensation isblown from the coil surface during cooling coilapplications. The extent of carryover is a function ofairstream velocity across the coil, fin spacing, fingeometry and material of construction. WhenE-Coating is applied to a cooling coil, carryover will occur at lower coil face velocities.Recommendations shown in Table A should be considered when selecting chilled water or DX coilsto ensure moisture carryover will be prevented.

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Field-Applied Coatings

Most field-applied sprayed-on coatings generally do not provide sufficient protection in corrosiveenvironments. Possible reasons for poor performance:

• Coil cleanliness is crucial for proper adhesion.Adequate field cleaning techniques are generally overlooked.

• Field application cannot ensure continuous coating of coil surfaces on multiple row coils. It is difficult to ensure uniform coating qualitythroughout the depth of the fin pack.

• Interior coil surfaces remain untreated whensprayed-on from unit exterior (often spray applicators cannot reach deep into the coilassemblies, leaving inconsistent coating).

Table A Maximum Recommended Face Velocity (FPM)*

*External fouling on cooling coils will adversely affect the maximum recommended face velocities. Data based on cleancoils with proper filtration and periodic cleaning of coil surfaces.

• Inconsistent coating thickness can minimize or negate coating protection. Recommendedcoating thickness cannot be ensured with fieldapplication on multiple row coils. Film thicknessmeasurements are generally overlooked.

• The coil must be void of corrosion prior to fieldapplication of the coating. Encapsulation ofexisting corrosion makes the coating ineffectiveby leading to continued deterioration and coating delamination.

E-Coated Material and Chemical Resistance

Chemical resistance of the E-Coating material isdescribed in the appendix, “E-Coating ChemicalResistance Guide.” Application of an E-Coated coilshould only be considered when the contaminant islisted in the Appendix guide. If the E-Coating isNOT resistant to the contaminant listed or if the contaminant is not listed in the appendix, applicationin this environment is not recommended. Contactyour Carrier representative for further guidance.

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Table B Industrial Contaminants

Contaminant

Sulfur Oxides

Nitrogen Oxides

Chlorine &Chlorides

Ammonia &Ammonia Salts

HydrogenSulfide

ChemicalSymbols

SO2

SO3

NOx

CI2

CIx

NH3

NH4

H4S

Type of Industry/Application

Pulp, Paper & Lumber PlantsIncineration Facilities

Fuel Burning Power GenerationDiesel/Gasoline Engine Operation

Pulp, Paper & Lumber PlantsIncineration Facilities

Fuel Burning Power GenerationDiesel/Gasoline Engine Operation

Cleaning Agent ProcessingWater Treatment Facilities

Salt Mining/ProcessingSwimming Pool Agents

Chemical IndustriesFertilizer Manufacturers

Waste Water Treatment FacilitiesAgriculture

Waste Water Treatment Facilities

Source ofContaminant

Process EmissionsProducts of Combustion

Process EmissionsProducts of Combustion

Process EmissionsWater Disinfection

Process By-Products

Process EmissionsProcess By-Products

Waste DigestionAnimal Waste & Fertilizers

Sludge Processing

PotentialColor of

Corrosion (on copper)*

BlackBlue

BlackBlue

BrownishYellow (Non-

hydrated)Green (hydrated)

Black

Black

Common industrial contaminants which are resistedby the E-Coated coils are shown in Table B.

* Discoloration is an indication of potential problems. However, identificationof contamination sources based on color may be misleading.

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SELECTION SUMMARY TABLES (TABLES C-H)

Protection Option Selection

Clearly identify the operating environment for theintended installation. Determine the severity of eachenvironmental factor associated with the installationsite. Choose the protection option based on the mostsevere environmental factor anticipated for thegiven site. As an example: the site is on the coastlineand the condenser coil is facing the ocean, but thereis no noticeable corrosion on other equipment. AnE-Coated Aluminum-Fin Copper-Tube option isrecommended. Always choose the option for themost severe environmental factor.

Note: Environments immediately adjacent to diesel exhaust,incinerator discharge stacks, fuel burning boiler stacks, orareas exposed to fossil fuel combustion emissions should beconsidered a Combined Coastal/Industrial application.Recommendations presented for Industrial and CombinedCoastal/Industrial Environments should be followed.

ACC - Acceptable application with corrosion protection in excess of required level

X - Recommended OptionNR - Not Recommended

Table C Coastal Environment Protection Option

Standard: Aluminum-Fin / Copper-Tube X NR NR NR NRMicrochannel Heat Exchanger X X NR NR NRCopper-Fin / Copper-Tube ACC ACC X NR NRPre-Coated Aluminum-Fin / Copper-Tube ACC X NR NR NRE-Coated Aluminum-Fin / Copper-Tube ACC ACC ACC ACC XE-Coated Copper-Fin / Copper-Tube ACC ACC ACC ACC X

Severity of Environmental FactorsLow Severe

Distance from CoastInland Coastline

Direction of Prevailing WindsFrom Unit to Coast From Coast to Unit

Corrosion Present on Other EquipmentNone Present Noticeable CorrosionCoil Option

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Standard: Aluminum-Fin / Copper-Tube X NR NR NR NRMicrochannel Heat Exchanger X NR NR NR NRCopper-Fin / Copper-Tube NR NR NR NR NRPre-Coated Aluminum-Fin / Copper-Tube ACC X NR NR NRE-Coated Aluminum-Fin / Copper-Tube ACC ACC X X XE-Coated Copper-Fin / Copper-Tube NR NR NR NR NR

Severity of Environmental FactorsLow Severe

Distance from CoastInland Coastline

Contaminant Concentration*0 ppm 100 ppm

Direction of Prevailing WindsFrom Unit to Coast From Coast to Unit

Corrosion Present on Other EquipmentNone Present Noticeable Corrosion

ACC - Acceptable application with corrosion protection in excess of required level

X - Recommended OptionNR - Not Recommended* “E-Coating Chemical Resistance Guide,” appendix.

ACC - Acceptable application with corrosion protection in excess of required level

X - Recommended OptionNR - Not Recommended* “E-Coating Chemical Resistance Guide,” appendix.

Table D Industrial Environment Protection Option

Table E Combined Coastal/Industrial Environment Protection Option

Standard: Aluminum-Fin / Copper-Tube X NR NR NR NRMicrochannel Heat Exchanger X NR NR NR NRCopper-Fin / Copper-Tube NR NR NR NR NRPre-Coated Aluminum-Fin / Copper-Tube ACC X NR NR NRE-Coated Aluminum-Fin / Copper-Tube ACC ACC X X XE-Coated Copper-Fin / Copper-Tube NR NR NR NR NR

Severity of Environmental FactorsLow Severe

Contaminant Concentration*0 ppm 100 ppm

Corrosion Present on Other EquipmentNone Present Noticeable CorrosionCoil Option

Coil Option

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Table F Urban Environment Protection Option

Standard: Aluminum-Fin / Copper-Tube X NR NR NR NRMicrochannel Heat Exchanger X X X NR NRCopper-Fin / Copper-Tube NR NR NR NR NRPre-Coated Aluminum-Fin / Copper-Tube ACC ACC X NR NRE-Coated Aluminum-Fin / Copper-Tube ACC ACC ACC X XE-Coated Copper-Fin / Copper-Tube NR NR NR NR NR

Severity of Environmental FactorsLow Severe

Pollution Levels/Population DensityLow High

Corrosion Present on Other EquipmentNone Present Noticeable Corrosion

Note: Environments immediately adjacent to diesel exhaust,incinerator discharge stacks, fuel burning boiler stacks, orareas exposed to fossil fuel combustion emissions should beconsidered a Combined Coastal/Industrial application.Recommendations presented for Industrial and CombinedCoastal/Industrial Environments should be followed.

ACC - Acceptable application with corrosion protection in excess of required level

X - Recommended OptionNR - Not Recommended

Coil Option

Table G Comparison of Protection Options with Standard Aluminum-Fin Copper-Tube Coil

Coil Option

E-Coated Copper Fin

E-Coated Aluminum Fin

Pre-coated Aluminum Fin

Copper Fin

Microchannel Heat Exchanger

Cost

----

---

-

--

=

Availability

-

-

=

=

=

CorrosionProtection

++++

++++

++

+

++

Weight

--

-

=

--

++

ThermalPerformance

-

-

-

=

++

+ Superior to Standard Coil= Equal to Standard Coil- Less Favorable to Standard Coil

Note: More than one + indicates factor is significantly better than standard coil;more than one - indicates factor is significantly less favorable than standard coil.

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Table H Advantages/Disadvantages of Protection Options

• High Thermal Efficiency• Lowest Cost• Light Weight

• Limited Corrosion Protection capability in corrosive applications

• Low Cost• Galvanic Decoupling

• Reduced Thermal Efficiency• Limited Protection Capabilities• Inappropriate in severely

corrosive environments

• Corrosion Durability in unpollutedmarine environment

• Effective Thermal Performance• Mono-metal Construction

• Highest Cost• Greatest Weight• Not effective in some

marine/industrial environments• Lower velocity limits require coil

to receive optimum airflow in cooling coil application

• Unexpected Corrosion due to local pollutants

• Flexible, Consistent, Durable• Superior Corrosion Protection• Complete Coil Encapsulation• Creates Barrier between all coil

surfaces and corrosive environments

Coil Option Advantages Disadvantages

Standard Coil

Pre-Coated Coil

• High thermal efficiency• Reduction in galvanic potential between

materials of construction• Environmentally sound• Lower refrigerant charge• Great structural robustness• Easy to clean• Easy coil replacement• Easier to repair than other all aluminum coils

•Limited corrosion protection capability in severe corrosive applications

•Field repair more difficult than copper tube coils

MicrochannelHeat Exchanger

Copper/Copper

E-Coating

• Higher Cost• Greater Weight

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COIL MAINTENANCE AND CLEANING RECOMMENDATIONS

Routine cleaning of coil surfaces is essential tomaintain proper operation of the unit. Elimination ofcontamination and removal of harmful residues willgreatly increase the life of the coil and extend thelife of the unit.

RELIABILITY TESTING/QUALITYASSURANCE AT CARRIER

As part of Carrier’s commitment to continuousproduct improvement and quality assurance, manytests can be performed to determine the level of corrosion protection for specific applications andenvironments.

Kesternich Testing

Moist SO2 testing is typically accomplished in whatis referred to as a Kesternich Chamber. The purposeof this cyclical testing is to simulate industrialatmospheres by introducing a known volume of SO2gas and exposing material to this while simultane-ously controlling the humidity at a high level for8 hours. This is followed by an ambient conditiondry cycle of 16 hours.

Steam Tests

The steam test was developed at Carrier to rapidlyevaluate the quality of various coatings. This testexposes coated metal panels to steam generated bya distilled water bath and heaters for various lengthsof time. Generally the exposure period is 48 hours,however, additional testing has been performed overother lengths of time to determine the total time toblister (a measure of the adhesive properties of acoating to a substrate).

Salt Spray Tests

Typically, salt spray testing is done according to theASTM Specification - B117. This cycle exposesmaterial to continuous salt fog commonly between500 and 2000 hours in duration. This isstrictly a comparative test as it does not correlatewell to actual atmospheric exposure.

Traditional salt spray testing has been performedaccording to the neutral salt spray test ASTMSpecification - B117 which uses a continuous 5%salt fog at 35 degrees C. This has been the acceptedcorrosion test method for more than 80 years, butgood correlation between the test results and corrosion seen in actual atmospheric exposures hasseldom been found. New test methods involvingcyclical exposures are being developed which canbe better correlated with actual atmospheric exposure results.

Kure Beach Studies

Coils and equipment are exposed to a coastal environment at a facility run by the LaQue Centerfor Corrosion Testing in Kure Beach, NC. Theatmospheric conditions are monitored at this sitewhere exposures have been done over the years at80-ft or 800-ft distances from the mean tide line.The testing performed here allows Carrier to determine actual performance of corrosion protection methods in a coastal environment. Theresults obtained from testing at the beach are used todevelop accelerated laboratory methods to simulatecoastal environments and to test methods for preventing corrosion.

Cyclic Corrosion Testing

Carrier utilizes a cyclic Corrosion Tester forenhanced testing capabilities at the LaQue Center.The Q-fog Model CCT600 is used to obtain morerealistic corrosion performance results than can beobtained from traditional steady-state exposures.

Carrier’s use of the cyclic Corrosion Tester allowsaccelerated testing methods to be developed morequickly. The chamber is able to run various programmed cycles such as the Prohesion™ cycle,GM exposures (GM9540PLB), Japanese automotivecycles, Japanese acid rain cycles and many othercyclic tests deemed necessary to provide meaningfulcorrosion data.

Prohesion™ Cycle Test Results Comparison

The corrosion performance of a baseline bare coil, apre-coated coil, three (3) post-coated coils and anE-Coated coil have been evaluated through

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Prohesion testing. This test subjects the coil to cyclicalexposure to highly corrosive solutions and regulateddrying time to simulate severely corrosive environ-mental conditions.

After 1000 hours of cyclical exposure, the corrosionperformances of the coils were evaluated by visualexamination and through heat transfer measurement.

The heat transfer performance factor G* is used toevaluate the thermal performance of the coils. TheG* factor shows a change in implied performancefor a coil compared to a baseline coil’s new impliedperformance. The higher G* value, the better thethermal performance.

Figure 14 shows the thermal performance resultsafter exposure for 1000 hours. It can be seen thatE-Coated coils have the best performance for thistype exposure. The other coil coatings fall well shortof the E-Coat performance.

Carrier Marine One Testing

A patented exposure cycle has been developed byCarrier Corporation to better simulate actual atmos-pheric exposure in an accelerated manner. Thismethod utilizes the combination of corrosive mediatogether with a cyclic exposure to spray, drying andhumidity at various temperatures which have beenfound to simulate exposure in a manner consistentwith actual exposure at Kure Beach, NC.

Fig. 14. Prohesion test results.

APPENDIX

E-Coating Chemical Resistance Guide

The coating materials used for E-Coat will withstandexposure to many corrosive atmospheres with theexception of formic acid and nitric acid. The E-Coatmaterial is resistant to fumes from the chemicalslisted below. However, Carrier does not recommenddirect coil immersion service for any of these chemicals. The chemical resistance guidelines weredetermined by a 24-hour spot test exposure of thechemical listed at ambient temperature conditions.Resistance was determined for these chemicals atthe concentrations identified.

Since resistance is dependent upon the application,environment, type of protection and other factors,your Carrier Representative should be consulted forrecommendations.

E-Coat is resistant to the following fumes:

Acetone Fructose OzoneAcetic Acid 99% Gasoline Perchloric AcidAcetates (ALL) Glucose Phenol 85%Amines (ALL) Glycol PhosgeneAmmonia Glycol Lither PhenolphthlaeinAmmonium Hydroxide Hydrochloric Acid 37% Phosphoric AcidAmino Acids Hydrofluoric Acid 30% Potassium ChlorideBenzene Hydrogen Peroxide 5% Potassium HydroxideBorax Hydrogen Sulfide Propionic AcidBoric Acid Hydrazine Propyl AlcoholButyl Alcohol Hydroxlamine Propylene GlycolButyl Cellosolve Iodine Salicylic AcidButric Acid Isobutyl Alcohol Salt WaterCalcium Chloride Isopropyl Alcohol Sodium BisulfiteCalcium Ilypochloric Kerosene Sodium ChlorideCarbon Tetrachloride Lactic Acid Sodium Hypochlorite 5%Cetyl Alcohol Lactose Sodium Hydroxide 10%Chlorides (ALL) Lauryl Alcohol Sodium Hydroxide 25%Chlorine Gas Magnesium Chloride Sodium SulfateChloroform Magnesium Sulfate SorbitolChromic Acid 25% Maleic Acid Stearic AcidCitric Acid Menthol SucroseCresol Menthanol Sulfuric Acid 25-85%Diesel Fuel Methylene Chloride Sulfates (ALL)Diethanolamine Methyl Ethyl Ketone Sulfides (ALL)Ethyl Acetate Methyl Isobutyl Ketone Sulfites (ALL)Ethyl Alcohol Mustard Gas StarchEthyl Ether Naphthol TolueneFatty Acid Nitric Acid 25% TriethanolamineFluorine Gas Olale Acid UreaFormaldehyde 27% Oxalic Acid Vinegar

Xylene

NOTE: All data, statements and recommendationsare based on research conducted by the E-Coat manufacturer and are believed to be accurate. It isthe responsibility of the user to evaluate the accuracy,completeness or usefulness of any content in thispaper. Neither Carrier nor its affiliates make anyrepresentations or warranties regarding the contentcontained in this paper. Neither Carrier nor its affil-iates will be liable to any user or anyone else for anyinaccuracy, error or omission, regardless of cause, orfor any damages resulting from any use, reliance orreference to the content in this paper.

E-Coat is NOT resistant to the following fumes:

Formic Acid • Nitric Acid

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Copyright 2006 Carrier Corporation www.carrier.com 04-581006-01 Printed in U.S.A. 04-06