J P C L J u l y 2 0 1 0 57www.paintsquare.com

Testing Coatings for Zebra and Quagga Mussel Control

R e s e a r c h N e w s

he U.S. Bureau of Reclamation,part of the U.S. Department of

Interior, functions mainly to deliverwater and hydropower in the 17 west-ern states. The Bureau maintains 476dams; produces 17% of thenation’s hydropower; suppliesirrigation water for 10 millionacres of farmland (25% of fruitsand 60% of vegetables producedin the U.S.); and serves 31 mil-lion people for municipal, resi-dential, and industrial wateruse.1 The Bureau’s infrastruc-ture consists of dams, powerplants, pumping plants, canals,pipelines, storage tanks, fishhatcheries, desalination plants,and water treatment plants. Thecomplex infrastructure is beingaffected by zebra and quaggamussel infestations.Zebra and quagga mussels are

freshwater fouling mussels thatattach themselves using byssal threads.Zebra mussels got their name from thedistinct striped pattern of their shell.The quagga mussel is also striped, butfades away towards the hinge. Quaggamussels are slightly larger than zebramussels, about the size of a thumb nail.Quagga mussels were first found in

western waters during January 2007 inLake Mead (Hoover Dam). Since then,the mussels have spread downstreamand into the Colorado aqueduct to Los

T Angeles, the Central Arizona Project toPhoenix, and a few other reservoirs inthe western U.S. The growth and repro-duction rate of mussels in warm watersof the southwest are up to six times per

year faster than observed rates in theGreat Lakes and Mississippi River.Currently, the greatest risk of mussel

infestations is in small diameter piping,(such as cooling water, HVAC, anddomestic water piping), fish screens,and intake structures. Due to the poten-tial impacts mussels will have onReclamation infrastructure, the Bureaubegan a research program on ways touse coatings to deter mussel attach-ment. This article reports on theresearch.

BackgroundThe Bureau of Reclamation’s primarymethod for corrosion protection ofmetal infrastructure to provide thelongest service life possible is protectivecoatings. Many coatings, including lead-

based primers, coal tar enamels, andvinyl resins, have lasted 50 to 60 yearswith minimal maintenance. Now, we areinvestigating coatings for mussel con-trol as well as corrosion protection.

The primary focus of the studyto date is the effectivenessantifouling, foul-release, or fluo-rinated powder coatings. Manydifferent antifouling coatings andtechnologies are available.2

Antifouling coatings rely on abiocide to deter the attachmentof fouling organisms. Types ofantifouling coatings include non-ablative, ablative, and self polish-ing. Non-ablative coatings areconsidered contact-leaching coat-ings where the binder does notdegrade. The biocide leaches intothe water, leaving the resultantexposed coating with a honey-comb appearance. Ablative coat-ings, considered controlled

depletion coatings, have two erosionfronts, a pigment dissolution front and abinder dissolution front. Self-polishingcoatings allow a controlled release ofbiocide at a constant rate—the polymerand biocide leach rate are approximate-ly the same, allowing for a constantantifouling performance. The self-polish-ing coatings have the longest service lifeof the antifouling coatings for ships.Foul-release coatings rely on low sur-

face energy chemistries that cause foul-ing organisms to release in flowingwater. The most common foul-releasebinders are based on poly (dimethylsiloxane) (PDMS). Fluoropolymer-basedfoul-release coatings are also available,but have a broader spectrum ofchemistries.

Continued

Allen Skaja, Ph.D. Coatings Specialist, U.S. Bureau of Reclamation, Denver, CO, USA

Editor’s Note: This article is based on a paper

the author presented at PACE 2010, the joint

conference of SSPC: The Society for

Protective Coatings and the Painting and

Decorating Contractors of America, held

February 7–10, 2010, in Phoenix, AZ.

Fig. 1: Aerial photo of Parker Dam. Red line indicates static conditions;yellow line indicates dynamic conditions.

All photos courtesy of the author

J P C L J u l y 2 0 1 058 www.paintsquare.com

In the mid 1990s, the U.S. ArmyCorps of Engineers determined that gal-vanizing and zinc metallizing alsodeterred the attachment of zebra mus-sels.3 Longevity of antifouling coatingsand zinc metallizing depends on flowrates, water chemistry, pH, water tem-perature, and salinity, whereas thelongevity of foul-release coatings arenot as dependent on these factors.The goal of the present research is to

find the coatings or technologies thatwork the best and longest for theBureau of Reclamation’s service condi-tions. Laboratory screening studies andfield coupon testing have been conduct-ed. The only way to determine if a coat-ing will successfullyresist the attachmentof fouling organisms isto have the coatingfield tested to verifylaboratory results.

Test Site and ExposureConditions

The Bureau’s coatingsresearch program forzebra and quagga mus-sel control began inJanuary 2008 atParker Dam on theColorado River. Thetest site was selectedbecause of its rapidlyincreasing mussel

infestation. There, quagga mussels canreproduce eleven months out of theyear because of the warm water. Thesite also provided areas for static (non-flowing water) and dynamic (flowingwater) testing.Most antifouling coatings are

designed for ships. Exposure conditionsfor ships vary with the purpose of theship, but generally, ships travel at highspeeds, 22 knots or higher, and thenmay sit for a period in static conditionsin port. Exposure conditions for metalat Parker Dam differ from those forships; at Parker Dam, in some areas,water is continually flowing (dynamic)through the trash racks, intakes, and

power house to allow water down-stream, while other areas see little or noflow. Velocities in dynamic areas varybetween 0.1 and 6 ft/sec (Fig. 1).The substrates for static condition

testing are one-square-foot steel plates,3⁄16 in. thick (Fig. 2). Three identicalplates were hung by a rope off the faceof the dam at 50 ft below the water sur-face. Steel floor grates for dynamic con-dition testing are 18 in. wide by 24 in.tall by 1 in. thick with one-inch spacingbetween grates (Fig. 3). The sampleswere tied behind the trash rack struc-ture at 40 ft below the water surface.The samples were tied with two ropesso they would not spin from water

flows through the gratespacing. Static anddynamic conditionswere tested becausedifferent facilities havedifferent requirements,and both conditionsmay exist at a site.Copper, brass, andbronze were used ascontrol samples to ver-ify that mussels do notattach to these metals.Carbon steel wasselected as a control todetermine the rate ofmussel attachment tothe surface.

R e s e a r c h

Fig. 3: Coated steel floor grate used for dynamic testing.

Fig. 2: Coated square foot steel plates used for static testing. From left toright: zinc-rich epoxy, galvanized, 85-15 zinc-aluminum metalized, 100% zinc

metalized, and copper metal.

Metal or Metallic Coatings Antifouling Coatings Foul release Coatings

1. Copper 9. Copper Metal filled 14. Fluoropolymer foulpolyester resin release coating

2. Brass 10. Cuprous oxide filled 15. Silicone foul releasecoating

3. Bronze 11. Ablative paint 16. Silicone epoxywaterborne coating

4. 90/10 Copper/Nickel 12. Zinc Omadine biocidecoating

5. Steel—uncoated 13. Proprietary biocidecoating

6. Galvanized Steel

7. 100% Zinc Metallizingon steel

8. 85/15 Zinc/AluminumMetallizing on steel

Table 1: Surface Materials and Coatings Tested May 2008

J P C L J u l y 2 0 1 0 59www.paintsquare.com

(800) 542-6646Fax (419) 542-6475www.modsafe.comEmail: modsafe@bright.net

Particulate removal

Liquid contaminate

removal

Deep charcoal bedremoves tastes, odors,gaseous hydrocarbons

Unique catalystremoves CO

Don’t Just Filter...Purify!

A I R I N

A I ROUT

Unique, patented low temperature catalyst purifies compressedbreathing air.• for continuous use to

remove carbon monoxide• no expensive desiccant

drying equipment needed• helps provide comfortable,

humidified compressed air tomeet Grade-D requirements

• by far, the most economical CO-removal alternative

Portable CO removal units from

8 SCFM to 50 SCFM; fixed systems up to 1000 SCFM.

CO monitor

Clickour

Reader

e-Cardatpaintsquare.com

/ricClick

ourR

eadere-Card

atpaintsquare.com/ric

Coatings and Materialsin the Test

The first round of testing began in May2008. Surface coatings and other sur-face materials investigated for musselcontrol were zinc metal coatings, coppermetal alloys, copper-based antifoulingcoatings, biocide antifouling coatings,and foul-release coatings, all in contactwith fresh water (Table 1).All coatings were applied following

the manufacturers’ recommendationsusing compatible corrosion-resistantprimers and compatible intermediatecoats. Suitability of coatings was basedon the performance criteria, shownbelow, developed through our experi-ence of properties needed for a coatingto be successful for our applications.1. Proven antifouling performance ofthe coating in fresh water or marineenvironments.2. Fouling resistance and/or easilycleaned.3. Must not release unacceptable lev-els of toxins into the environment, i.e.meet EPA regulations for fresh waterand canals for irrigation.4. A minimum service life for twoyears with less than 10% mussel attach-ment on testing substrates.5. Fouling resistance in static anddynamic flowing conditions.6. Commercially available7. Sufficient corrosion protection8. Suitable for use with or withoutcathodic protection9. Capable of being applied at 110 Fand at a minimum of 40 F with humidi-ty levels between 5% and 75%10. Fully cured and hard for handlingpurposes. Coatings may be subject to amaximum temperature of 120 F andcannot get tacky at these high tempera-tures.

ResultsAfter six months of exposure, it wasclear that some materials and coatingsworked while others did not. Only four

Continued

R e s e a r c h

J P C L J u l y 2 0 1 060 www.paintsquare.com

coatings remained in the study after sixmonths, and only three coatingsremained in the study in just over ayear of exposure (Table 2).

Discussion of ResultsMany coatings did not perform well forseveral reasons. For instance, exposureconditions are not the same as the ship-

ping industry. Flow rates, water chem-istry, pH, salinity, temperature, andrelated conditions play a key role in theleach rate of the biocides in antifouling

R e s e a r c h

Table 2: Materials and Coatings Results

Metals or Metallic Coatings Tested1. Copper

2. Brass

3. Bronze

4. 90/10 Copper nickel

5. Steel—uncoated

6. Galvanized steel

7. Zinc metallizing on steel

8. Zinc/aluminum metallizing on steel

9. Copper metal-filled antifouling polyester

10. Cuprous oxide antifouling coating

11. Ablative antifouling paint

12. Zinc omadine biocide antifouling paint

13. Proprietary biocide antifouling paint

14. Fluoropolymer foul-release coating

15. Silicone foul-release coating

16. Waterborne silicone epoxy foul-release coating

PlatesNo mussels/no biofilm or algae growth.Remains in study after 12 months.Few adults/ few juveniles/ minor.Remains in study after 12 months.Few mussels.Remains in study after 12 months.Heavily fouled.Discarded at 4 months.Heavily fouled.Discarded at 7 months.Few mussels at 7 months; many mussels at12 months.Discarded at 12 months.Many mussels.Discarded at 7 months.Many mussels.Discarded at 7 months.Few mussels, no biofilm and algae growth.Remains in study after 12 months.Bottom panel had many mussels attached;other 2 panels had only a few musselsattached, minor biofilm and no algaegrowth.Discarded at 7 months.Several adults on bottom panel; few adultson other 2 panels, minor biofilm, no algaegrowth.Discarded at 12 months.Few adults/ minor biofilm or algae growth.Discarded at 7 monthsSeveral adults attached on bottom panel thatwas in the mud line; no juveniles, minorbiofilm, no algae growth.Discarded at 7 months.Few mussels with easy removal except indefected or damaged coating areas; minorbiofilm and algae growth.Remains in study after 12 months.No mussels; damage from concrete.Remains in study after 12 months.Heavily fouled.Discarded at 7 months.

GratesNot tested.

Not tested.

Not tested.

Not tested.

Heavily fouled 100% blockage.Discarded at 7 months.Less than 10% blockage at 7 months;80% blockage at 12 months.Discarded at 12 months.50% blockage.Discarded at 7 months.75% blockage.Discarded at 7 months.Few mussels, some biofilm.Remains in study after 12 months.Few mussels, Druse (clumpsof mussels), minor algae,25% blockage.Discarded at 7 months.

Many mussels, 25% blockage.Discarded at 12 months.

Mussels, 20% blockage.Discarded at 7 months.Few mussel, 25% blockage.Discarded at 7 months.

No mussels; foul-release coat partiallydelaminated, some biofilm and algaegrowth, damage from concrete.Remains in study after 12 months.No mussels; damage from concrete.Remains in study after 12 months.100% blockage; is not easier to removethan the other coatings.Discarded at 7 months.

J P C L J u l y 2 0 1 0 61www.paintsquare.com

KTA-Tator, Inc. • 115 Technology Drive • Pittsburgh, PA 15275PH-412.788.1300 • FX-412.788.1306

www.kta.com • www.ktagage.com

The KTA Survey GroupBacked by an In-house Team of Industry Experts

Comprehensive Surveys of Coating Condition• Percent and Type of Deterioration• Physical Condition – Adhesion, Thickness• Existing Coating Type• Toxic Metal Content

Maintenance Painting Recommendations*• Painting Strategy and Year• Surface Preparation/Coating Brand Names• Opinion of Probable Cost

*KTA CAPP® System software used for large, complex projects.

When you hire KTA, you hire an entire team of industry experts

Clickour

Reader

e-Cardatpaintsquare.com

/ricClick

ourR

eadere-Card

atpaintsquare.com/ric

coatings and zinc metals. Coatingchemistries for antifouling and foul-release are vastly different. The self-pol-ishing or ablative degradation mecha-nisms vary drastically with fresh waterversus sea water. It is also possible thatthe manufacturers’ testing conditionswere not the same as ours.The coatings that survived six

months of continuous immersion werean ablative biocide antifouling, a coppermetal-filled polyester, a fluoropolymerfoul-release, and a silicone foul-release.

Metals or Metallic Coatings:The copper, brass, and bronze controlsremain mussel free for more than oneyear. The steel control sample was com-pletely blocked from mussels at seven

months (Fig.4). The 90/10copper/nickelwas selectedas an alterna-tive metal fort e s t i n gbecause it isstronger andmore corro-sion resistantthan copper.

In sea water, the 90/10 copper/nickelalloy is used as a construction materialthat resists fouling.4 However, it fouledheavily at the test site after just fourmonths of exposure (Fig. 5).Galvanizing, 100% zinc metallizing,

and 85/15 zinc/aluminum metallizingwere included because of the previousArmy Corps of Engineers study.Because of the water chemistry, thezincs were passivated, possibly by zinccarbonate, and the zinc ions were notexposed at the surface to prevent settle-ment. Metallizing fouled at a faster ratethan galvanizing because of the surfaceroughness. (Fig. 6)

Antifouling Coatings:The copper metal-filled polyester coated

Continued

R e s e a r c h

Fig. 4: Uncoated steel floorgrate in dynamic conditionsat 7 months of exposure.

J P C L J u l y 2 0 1 062 www.paintsquare.com

biodegrades relatively quickly. It usesthe same binder as the zinc omadinecoating and also melted in the desertheat. The panels were pried apart with ascrew driver but were still placed in thewater for testing. The product fouledmore than 10% at seven months, possi-bly because of surface roughness.

Foul-Release CoatingsThe fluoropolymer foul-release coating

is non-toxic. Ithas remainedmussel free forover one yearand remains intesting. Thiscoating requiresa special tie coatand is relativelysoft, so the fluo-ropolymer coat-ing probablydoes not with-

stand gouging or rubbingof debris. The softness pre-sents a problem becauseReclamation is looking atusing these coatings ontrash racks, which willhave debris such asbranches, trees, weeds,and garbage. Anotherpotential problem encoun-tered is that the productrequires a minimum of30% relative humidity tocure properly. Some areasin the western U.S. haverelative humidity levels of 15% orlower for at least part of the year, so

localized humidifiers may be requiredto apply the fluoropolymer.The silicone foul-release coating is

non-toxic but slowly releases its lowmolecular weight silicone oils. This coat-ing has remained mussel free for overone year and remains in testing. Thiscoating also requires a special tie coat.The silicone is also relatively soft andprobably does not withstand gouging orrubbing of debris. The curing mecha-nism is a chemical cure and does notrely on moisture in the atmosphere.There do not appear to be any applica-tion issues related to the environmentalconditions in the southwest deserts.The silicone-epoxy waterborne coat-

ing is non-toxic, durable, and slick.However, the panels coated with it hadmussel attachment levels equal to thesteel plate controls. It was determinedthat the mussel attachment was just ashigh as a conventional epoxy coatingand there was no benefit to continue

testing, so these panelswere withdrawn at sevenmonths.

Current TestingIt has been a concern fromthe start that foul releasecoatings may be damagedeasily during handling andinstallation, and fromdebris once installed.Reclamation, therefore,looked for coatings thatwould be more durablethan the ones studied.

Extensive literature reviews of the U.S.Naval Research Laboratory (NRL) doc-

uments were conducted because oftheir pioneering research withfoul-release coatings for ships.5,6,7

Evaluation of the physical proper-ties of some of the polymers in theNRL documents indicated thatNRL appeared to be investigatingonly relative adhesion for marineorganisms.7 According to NRLresearch published, poly (dimethyl

R e s e a r c h

grate at one year of service had a fewmussels attached, with only about2–3% coverage. This product is nonab-lative; therefore, the binder matrixremains while the copper slowly leach-es into the water. The service life willdepend on the flow rate. At the time ofthis writing, the service life is unknownin static and dynamic conditions withthis particular product. It remains in thetesting past one year.The cuprous

oxide coating is ana c r y l i c - b a s e dantifouling coating.It produced mixedresults: in staticconditions, twoplates were musselfree while oneplate was coveredin mussels. Indynamic condi-tions, about 25% ofthe grate was covered with mussels,which does not meet the performancecriteria.The mechanism of the ablative coat-

ing is unknown. However, the majorityof these types of coatings slowlyhydrolyze or react with salts in thewater, slowly eroding the coating. Thisparticular product was withdrawnfrom the test at one year because it hadover 10% mussel attachment in flowingconditions.Zinc omadine is a biocide used in

some antifouling coatings and otherproducts. Unfortunately, it is unclear ifzinc omadine actually works for musselcontrol because this product originallymelted and glued all the panelstogether in the 115 F heat. Thepanels were pried apart with ascrew driver but were still placedin the water for testing. The prod-uct fouled more than 10% at sevenmonths, possibly because of sur-face roughness.A proprietary biocide is gaining

some major attention because it

Fluorinated Powder Coatings

1. Poly vinylidene fluoride (PVDF)

2. Ethylene chloro trifluoroethylene copolymer (ECTFE)

3. Ethylene tetrafluoroethylene copolymer (ETFE)

4. Perfluoroalkoxy (PFA)

5. Fluorinated ethylene propylene (FEP)

Table 3: Fluorinated Powder Coatings Tested May 2009

Fig. 5: 90/10 Copper/nickel alloy in static conditionsafter 4 months of exposure.

Fig. 6: 100% zinc metallizedgrate at 7 months exposure.

J P C L J u l y 2 0 1 0 63www.paintsquare.com

Clickour

Reader

e-Cardatpaintsquare.com

/ricClick

ourR

eadere-Card

atpaintsquare.com/ric

siloxane) was the best polymer forrelease properties even though it didnot have the lowest surface energy.7

Reclamation decided to investigatesome of these polymers for resistingmussel settlement and durability infresh water applications. Reclamationalso decided that polymer sheets wouldnot be useful as an end product; there-fore, fluorinated powder coatings withsimilar chemistries would be investigat-ed.The second round of testing was

started in May 2009, and aimed atinvestigating fluorinated powder coat-ings (Table 3). These fluorinated powdercoatings are commercially available.The coatings would require metalworkto be small enough to fit into an indus-trial oven. These coatings are muchmore durable than the two foul-releasecoatings currently in testing. Initialresults at six weeks showed some juve-nile mussel attachment on two of thecoatings while the other three coatingsremained mussel free. Interim resultsto determine the ability of these coat-ings to resist the attachment of musselswill be discussed in a future paper.

Further TestingFurther testing involves evaluation ofsilicone foul-release coating, fluoropoly-mer foul-release coating, epoxy siliconefoul-release coating, epoxy filled withPTFE powder, vinyl ester with a lowcoefficient of friction, and a fluorinatedpolyurethane. Panels and grates withthese coatings were installed inNovember 2009, and some results willbe discussed in a future paper. In addi-tion, other products were incorporatedinto the testing in May 2010.

ConclusionThe Bureau of Reclamation has beenevaluating commercial coatings andmaterials to deter the attachment ofzebra and quagga mussels. The ultimategoal is to find coatings or materials to

Continued

R e s e a r c h

Now Available forAmazon Kindle®

the

SSPCPocket Guide toCoating Information

For the first time, the popular SSPC Pocket Guide to Coating Information is available in ebook format.Users can download the ebook from Amazon.com® and read it on their Kindle® !

The all-new ebook edition features the same content found in the printed version, including those charts, standards, andcalculations most frequently needed during surface preparation and coating application.Also features NEW content updated for 2010.

All this for only $15.00. To purchase, simply browse to www.amazon.com and search on "sspc pocket guide"

PUBLICATIONS

theAmazoNow A

®on Kindlevailable forA

CoatinPockeSSPC

ing Informationet Guide toC

n

Click our Reader e-Card at paintsquare.com/ric

J P C L J u l y 2 0 1 0 65www.paintsquare.com

Have a new Surface Prep project but don’t want to invest in new equipment? Try renting! From 40k waterblasters to spinning nozzles. Blasting mowers to lances, water guns to safety wear. FS Solutions centers carry high quality Jetstream units for rent or purchase as well as all of the parts and accessories for your surface prep application.

Long Beach, CA 866.515.9891Gonzales, LA 225.647.0660

We’ve Got You CoveredPurchase or RentBirmingham, AL 800.822.8785Toledo, OH 888.415.7368

Call today for pricingand availability.

Image courtesy of Hydro-Klean, Inc.

Clickour

Reader

e-Cardatpaintsquare.com

/ric

obtain the longest service life musselfree. Reclamation has tested one metalalloy and eleven coatings. Only threecoatings remain mussel free after oneyear in service. Current investigationsare looking for coatings with greaterdurability that still prevents musselattachment.

DisclaimerThe results of this research are site spe-cific; some coatings may perform well inother service conditions, waterchemistries, and service environments.The following data should not be usedfor advertising or promotional purpos-es. The information should not be con-strued as an endorsement of any prod-uct or firm by the Bureau ofReclamation, Department of Interior, orFederal Government.

References1. www.usbr.gov/facts.html2. Claire Hellio and Diego Yebra,“Advances in Marine AntifoulingCoatings and Technologies,”Woodhead Publishing Limited, 2009.

3. US Army Corps of EngineersWaterways Experiment Station,Technical Note ZMR-2-01.

4. http://www.cda.org.uk/megab2/corr_rs/pub-157-preventing-biofouling-withcopper-nickel.pdf

5. Advanced Nontoxic Fouling ReleaseCoatings NRL/PU/6110-99-388,1999.

6. Robert Brady, “Fouling- releaseCoatings for Warships,” DefenseScience Journal, Vol. 55, No. 1 Jan.2005 pp. 75–81.

7. Robert F. Brady, Jr., “Propertieswhich influence marine fouling resis-tance in polymers containing siliconand fluorine,” Progress in OrganicCoatings 35 (1999) pp. 31–35.

8. Robert Brady, “Clean Hulls WithoutPoisons: Devising and TestingNontoxic Marine Coatings,” Journalof Coatings Technology, 2000, vol. 72,No. 900, pp. 44–56.

R e s e a r c h

Allen Skaja earned his BS in Chemistry in 2000 and Ph.D. in

Coatings and Polymeric Materials in 2005 from North Dakota State

University. He joined the Bureau of Reclamation in June 2005 as a

Coatings Specialist. Immediately he began evaluating coatings for

corrosion protection. In Jan. 2008, he began testing coatings to

deter the attachment of zebra/quagga mussels.