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ATI WAH CHANGPO BOX 460ALBANY, OREGON 97321 USA

W W W . A L L E G H E N Y T E C H N O L O G I E S . C O M

5 Fabricating with Reactiveand Refractory MetalsA Basic Understanding

INSIDE THIS ISSUE

3 United Titanium, Inc.Precision Machining of ExoticAlloys for Critical Parts

V O L U M E 3 0 N U M B E R 4F O U R T H Q U A R T E R 2 0 0 9A N A T I P U B L I C A T I O N

P R O D U C E R S A N D F A B R I C A T O R S O F R E A C T I V E A N D R E F R A C T O R Y M E T A L S A N D C H E M I C A L S

6 Corrosion SolutionsTitanium Alloys for RenewableEnergy Applications

Page 2

Vacuum Pump Project Team (top row left to right)Randy Scheel and Aaron Fosdick (ATI WC), Don Travisand Ian Karas (SIHI). Bottom row left to right: JohnElder (ATI WC) and Bryan Jensen (Rogers Machinery)

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Zirconium Pump Sets New StaUFIRSTHAND

Zirconium Pump Sets New Standardfor ATI Wah Chang Sponge PlantBY: KIRK RICHARDSON — ATI Wah Chang

“Tribal knowledge” is a good thing untiltoo many members of the “tribe” retire.Potential loss of institutional knowledge wasrecently on John Elder’s mind as the ATI WahChang Engineer planned for replacement ofkey processing equipment as part of thecompany’s chemical plant expansion project.

Elder’s challenge involved a relatively smallbut important vacuum pump in the zirconiumproduction process. Ironically, what keepsthis equipment from withering away in thesevere service environment are its zirconiumcomponents. Plant Engineering and ChemicalOperations decided that it would be wise todevelop a standard, repeatable method ofmanufacturing the pumps.

Wah Chang machinists originally builtthe equipment about 30 years ago. “Wehave had those in service for all that time,”he says, adding that they are pulled andrepaired as needed. “This specific applicationhas a lot of corrosion out there, so it’s notlike we could bring in the regular cast ironliquid ring.”

According to Division Director RandyScheel, acid and temperature spikes in thesponge-making process can corrode manyalloys. “Corrosion can cause the pumps tonot achieve required vacuum levels,” heexplains. Resulting leaks in a system couldallow air where it’s not wanted and lead tosignificant problems, according to Scheel.

Though it helps keep the pumps fromleaking over extended periods, zirconium isnot a magic bullet. Even one of the mostcorrosion resistant alloys in the metals familywears down over time and needs to befactored into plant maintenance plans. “Theyget rebuilt often to replace pump seals andbearings, but not the zirconium components.”reports Elder.

Rebuilt from old blueprints, according toElder. “We’ve got some guys in the shop thatare really talented and can take those printsand build a pump out of it,” he says. “Theycan work miracles with that kind of print, butthose guys have been around for awhile, andwhen you lose one or two of them to

retirement, you lose that. For us to rely ontribal knowledge with the next generationcoming aboard, it’s really scary.”

A facility expansion project offered theperfect opportunity to look for a long-term,standard solution. Elder pulled together ateam that included longtime ATI Wah Changequipment supplier Rogers Machinery andSIHI Pumps Limited. According to BryanJensen, Rogers’ Eugene Branch Manager, thecompany has supplied ATI with aircompressors, rotary screws, dryer equipment,filtration equipment for air compressorsystems, and a number of othermanufacturing-critical components. “Weturned around the skid in a couple of weeksfrom the time we got the pump in, got amotor for him and everything fabricated upto the specs required and got the final productto you down at your facility,” reports Jensen.

It took a team effort and an existing pumpdesign to make the project a success. “Wetook a standard design from SIHI, and wedidn’t have to go through the heartache oftrying to design in-house from old prints andrelay that to so many people,” says Jensen.“They have their off-the-shelf design; theonly difference is that we were implementingin zirconium.”

That was a big, but not insurmountabledifference. Ian Karas, an Applications Engineerwith SIHI, mentions that the company hadworked with titanium before, but neverzirconium. “This is a new metal that we havenever machined in-house,” reports Karas. “Wetook our standard design, but made specialdrawings in terms of the machining tolerancesto ensure a precise as fit as possible. A lot ofthe tolerances got smaller. From a machiningstandpoint, it was done to a very tight standardand very tight tolerance, so that we did meetthe requirements.”

SIHI also simplified the pump in theprocess. “Typically when we get into thesetypes of special metallurgy and special designs,we steer away from that two-stage designdue to the complexities of the liquid ringvacuum pump design,” according to Karas.“We recommend a single-stage design, which

2 FOURTH QUARTER 2009 OUTLOOK

SIHI manufactured this corrosion resistant zirconium vacuum pump to withstand acid and temperaturespikes in ATI Wah Chang’s challenging sponge-making process.

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aUnited Titanium, Inc. Turns ExoUnited Titanium, Inc. Turns Exotic Alloysinto Critical Parts

FOCUS ON FABRICATION

“ATI Wah Chang has been a good partner,”says Gray. “We developed a proprietary heattreating process for zirconium parts, to relievestress and develop an oxide coating to helpwith erosion resistance. At first we had somedifficulties, and consulted ATI Wah Changengineers. It turned out the reason was thatwe needed a different solvent to moreeffectively clean the parts prior to heattreating. ATI Wah Chang engineers helpedus find a solvent that did the job. We havenot had heat treating problems since then.”

The most difficult zirconium parts UnitedTitanium makes are wear rings and extremelyclose-tolerance pump housings. Precision ischallenging with tolerances as close as +/-0.0002 inch, even though zirconiummachines well.

Tantalum provides a combination ofproperties not found in many refractory

neutrons. These properties prompted the U.S.Navy to use zirconium in water-cooled nuclearreactors as cladding for uranium fuel.

Today, a high proportion of zirconium isused in water-cooled nuclear reactors; thenext largest use is in chemical-processingequipment. Additional applications includeflashbulbs, incendiary ordnance, and getteringcontaminating gases in sealed devices suchas vacuum tubes.

Since 1962, United Titanium, Inc. has beenknown for its capabilities in precisionmachining and upsetting of titanium,zirconium, nickel alloys and tantalum for criticalapplications in the aerospace, power generation,chemical processing and medical industries.

“We regularly make parts from alloys thatmost job shops aren’t familiar with,” saysCharlie Gray, vice president and generalmanager at United Titanium “We specializein exotic alloys for critical parts in corrosiveand/or strength environments, and we leavethe commodity alloys to others. We fill ordersranging from several thousand to just a handfulof parts.” Gray should know, having workedat United Titanium for 44 years.

“We’ve been partnering with ATI WahChang for 40 years,” he adds, “beginningwith 702 and 705 zirconium, and latertantalum. We use zirconium for fasteners,fittings, and precision pump components. Thetantalum is used for parts that go into missiles.”

Zirconium is ductile and has usefulmechanical properties similar to those oftitanium and austenitic stainless steel.Zirconium also has excellent resistance tomany corrosive media, including superheatedwater, and is transparent to thermal energy

United Titanium Inc. has a modern facility measuring 132,000 square feet. It houses fastener manufacturingas well as the service center.

About United Titanium, Inc.

United Titanium Inc. is owned by Mike Reardon, who purchased it in 1974. The companyhas 130 employees, a number that has been stable since about 2005. Products includeprecision-machined components, fasteners, fittings, and mill products. Their service centeralso provides services such as shearing, welding, saw cutting, machining, and waterjetcutting. The company was selected by the Wooster Chamber of Commerce as Businessof the Year in 2007.

[ continued on page 4 ]

3OUTLOOK FOURTH QUARTER 2009

is a different model than what a lot of peoplemay have been used to here.”

A successful dry run followed by monthsof trouble-free operation, and Elder is soldon the solution. “SIHI Pumps (Limited) hadtheir own patent and a very nice product thatwe could buy from them with a warranty

and get our vacuum pumps that we need inan accelerated schedule,” he says. “With ourmachine shop bogged down, it didn’t reallyhave the time to make this equipment, nordid we really want them to.”

Scheel adds that the breakthrough couldbenefit others. “While the zirconium pump

is a solution for ATI Wah Chang’s plant, theSIHI design could be a solution in otherprocessing environments that requirecorrosion resistance,” he explains. “It mayjust be a matter of letting people know thatthere is another option available.” For moreinformation, visit www.sihi-pumps.com. a

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United Titanium, Inc. Turns ExoUnited Titanium, Inc. Turns Exotic Alloys into Critical Parts[ continued from page 3]

adds. “We even have a number of CNCmachines that we have developed in-house toservice specific customers, especially for medicaland dental implants.”

Medical screws and implants of many sizesare a major part of United Titanium’s business.Titanium Grade 23 (Ti-6Al-4V) ELI is used mostfrequently for medical components by UnitedTitanium because of its high strength andbiocompatibility. Titanium is completely inertand immune to corrosion by all body fluidsand tissue, and is thus completelybiocompatible. In addition, when bone-formingcells attach themselves to the titanium implant,a structural and functional bridge formsbetween the body’s bone and the new implant.

Carlos Weekley formed United Titaniumback in 1962 in the early years of the titaniumindustry. He saw the need for titaniumfasteners, and started the company in an oldfeed mill in Shreve, Ohio, to focus on thatmarket. His first customer was ChemcutCorporation, which needed pump shafts, coils,and fasteners for chemical process equipment.They are still a customer today.

Another early customer was NASA, forwhich United Titanium supplied fasteners forthe Pioneer space program. NASA still relieson the company for a variety of satellite andspacecraft parts.

Located since 1985 in Wooster, Ohio,United Titanium occupies 132,000 squarefeet and includes a fastener facility and anewly formed service center.

“We are the largest stocking distributor ofzirconium fittings in the world,” says StephenMcLain, International Sales Manager, ServiceCenter. “In our distribution center, we stocktitanium Grades 2 and 7 and zirconium in awhole raft of forms, including sheet, bar, plate,pipe, and fittings, in a wide range of sizes.”

For fasteners they stock a wide range oftitanium, zirconium, Inconel 686, and othernickel-cobalt alloys, including some superduplex stainless steel. “The more demandingthe application and the more exotic the alloy,the better we are at differentiating ourselvesfrom everyone else,” says Gray.

For more details about United Titaniumproducts and services, please visitwww.unitedtitanium.com. a

in chemical process equipment such as heatexchangers, condensers, thermowells, andlined vessels. This equipment handles nitric,hydrochloric, bromic, and sulfuric acids, orcombinations of these acids with many otherchemicals. Spinnerettes for extruding man-made fibers constitute another importantapplication of tantalum.

Special tantalum screws were one of thebiggest challenges for United Titanium. “Theywere tough to make because we were tryingto forge a head on a very small shaft (0.071-inch diameter) of tantalum,” explains salesmanager Doug Meigs. “But the head requiredmore material than can normally be controlledin upset forging. The piece must be hit perfectlydead center with specially designed tools tomake it right. It took weeks and weeks toproduce the required number of perfect parts.”

Such perfection is standard for UnitedTitanium products. “We are proud of ourquality,” says Meigs. “Our manufacturingengineers and quality control departmentsdo whatever it takes to ensure we ship qualityparts. We are just as proud of our reputationfor on-time delivery.”

They manufacture parts as small as 00-96 screws and dental implant components.“Each one is inspected,” says Meigs, “allunder a microscope!”

“We are able to machine such parts becausewe constantly upgrade our equipment,” he

metals. It has a high melting point (2296°C,or 5425°F), tolerance for interstitial elements,and reasonable modulus of elasticity. Tantalumalso possesses excellent room-temperatureductility, with >20% tensile elongation, andis readily weldable.

Because of its high melting point, tantalumis used for heating elements, heat shields, andother components of vacuum furnaces. It hasalso been selected for specialized aerospaceand nuclear applications, as well as forprosthetic devices in contact with body fluids,and as an alloy component in superalloys.

Sizable quantities of tantalum are used

4 FOURTH QUARTER 2009 OUTLOOK

F

United Titanium, Inc. makes a range of precisionfasteners of a wide variety of alloys.

Zirconium fittings are among the many product lines United Titanium, Inc. manufactures and supplies.

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5OUTLOOK FOURTH QUARTER 2009

oFabricating with Reactive andFabricating with Reactive and Refractory Metals

FABRICATION

BY: BRETT KRUEGER — ATI Wah Chang

Generally, reactive and refractory metals areformable, can be cut and welded, and likeother metals, they have a wide variety of bendradius limits. It is important to understandthese constraints for each alloy before startingany forming operations. When forming aparticularly complex shaped part or a piecethat has a tight bend radius, the use of heatto warm the part will greatly enhance itsmovement. Just be aware of the 425°Ctemperature ceiling. If processing requirestemperatures greater than 425°C, subsequentcleanup may be necessary to remove absorbedatmospheric surface contaminants. Thesemetals can be formed dry in a press break orforge, for example, and can also be drawninto shapes with forming dies. The use ofdrawing or dry film lubricants will help reducethe tendency to damage the metal surface.

Differences in machining practices frommore common metals include a greatertendency to gaul, smear and work harden(similar to stainless steel). Because of this,low cutting speeds and feeds provide thebest performance. Chip management is alsodifferent. It’s not uncommon to produce achip that is stringy, continuous and difficult

For as long as reactive and refractorymetals have been accessible, the questionof how to manufacture parts or structureshas perplexed fabricators, particularly thosewho are accustomed to more commonmetals, such as steel, stainless, nickel,aluminum or copper. Understandably theremay be some apprehension, but considerthat all these materials are metals and thatthey can be processed by virtually all modernmetal working technologies (albeit with somespecial considerations). With a basicunderstanding of material characteristics,fabricators can quickly develop processingtechniques that allow them to produce parts.

Let’s establish what metals comprise thesetwo groups. For the purpose of a generaloverview, reactive metals are those that meltbelow about 1750°C and include titaniumand titanium alloys. Metals that melt abovethis temperature are considered refractoryand include zirconium, vanadium,molybdenum, hafnium, niobium, tantalum,tungsten and their alloys.

In all cases, whether working with areactive or refractory metal, two veryimportant points need to be understood thatdifferentiate these materials from morecommon metals:

• First, at temperatures above about 425°C,all reactive and refractory metals becomesusceptible to contamination from carbon,oxygen, nitrogen, and hydrogen. Ifsufficient amounts if these elements areabsorbed into the metal, it can result ina loss of ductility, increased susceptibilityto corrosion and can lead to prematurefailure of the component.

• Second, metal cleanliness and surfacecondition prior to processing is critical.Surface contaminants such as dirt, oils,iron flakes, grinding swarf and gougemarks that have imbedded particles needto be removed. Processing grimy ordamaged metal can produce areas ofhigh stress concentration and increasedmetal corrosion. Thoroughly cleanedmetal is fundamental to producing highquality parts.

to break. In some applications chip windingtools have proven to be highly successful. Tohelp control chip production, machine withsharp tools that have high cutting rake angles,avoid chip pileup at the cutter point and usemachining coolants. These metals are toughand will require high torque (at low RPM),ridged machine tools with solid fixture setups.

Welding requires the incorporation ofargon and/or helium shielding gas into theprocess. Trailing and root backing shields arenecessary to protect the molten pool andsurrounding heated metal. Without ashielding gas component, the metal willbecome embrittled from atmosphericcontamination. The most common processesare GTAW and GMAW, however plasma,laser, or electron beam welding have allproven successful.

It’s always good practice to investigateand identify all special processing parametersof any unfamiliar metal before starting aproject. ATI Wah Chang is a tremendousresource that can help provide guidance whenworking with reactive and refractory metals.For more information, contact TechnicalServices at 541-967-6977. a

An example of the GTAW process (gas tungsten arc welding) during ATI Wah Chang’s Annual Welding Seminar.

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5OUTLOOK FOURTH QUARTER 20096 FOURTH QUARTER 2009 OUTLOOK

conditions, steel will likely be replaced withmaterials like titanium. Titanium’s corrosionresistance and strength make it ideal forproduction wells and heat exchanger tubing.

Typical convective hydrothermal energyreaches temperatures in the 260-330°C range.New advances in the industry could lead tomagma-based energy where temperaturesexceed 500°C. Alaska and Hawaii are likelylocations for this to start[2]. These are idealconditions for titanium alloys with the additionof a Platinum Metal Group (PMG).

Tubular products are not the only titaniumforms used in the geothermal industry. Highstrength, corrosion resistant metals arerequired for parts such as springs, snap-ringsand other important components.

NuclearWhen it comes to materials used in nuclearpower production, zirconium gets most of thecredit. However, there are areas in the processwhere titanium is used, such as the steamturbine condenser (typically Ti Grade 2). Insome nuclear applications, Ti Grade 2 doesnot provide sufficient corrosion resistance.One such case is drip shields used in spentfuel repositories.

GeothermalDownhole conditions for geothermalapplications can range from moderate tomost severe. The Salton Sea wells in SouthernCalifornia represent probably the most severedownhole environment encounteredanywhere in the world. Companies tappinginto this natural resource may use steel fordrilling exploration holes, but they rely ontitanium, such as Ti Grade 29 (Ti 6-4 ELI w/Ru), to replace the steel that can fall apartafter 18 months of service.

Most corrosion in geothermalenvironments and other similar applicationsdescribed previously is caused by seven keycorrosive species[1]:

• Oxygen• Hydrogen Ion• Carbon Dioxide• Hydrogen Sulfide• Ammonia• Chloride Ion• Sulfate Ion

Depending on the location, certain metals willbe suitable for the environment. As the industryprogresses to deeper and more corrosive

Titanium for Renewable EnergTitanium for Renewable Energy Applications

CORROSION SOLUTIONS

In addition to being a material of choicefor engineers designing airplanes andmedical implants, titanium has manyother applications. One niche in whichtitanium alloys have not been used widely isin renewable energy production.

This article takes a look at the potentialapplication of corrosion resistant titaniumalloys in a challenging production environmentthat is becoming critical to meeting the world’senergy needs.

APPLICATION AREASTitanium alloys have been used for over 40years in many corrosive applications such aschemical processing, refineries, metal finishingand pulp and paper. More recently, these alloyshave been used in the power generationindustry, such as geothermal wells and oil andgas applications requiring higher strengthsand good corrosion resistance. The conditionsencountered in these geothermal, oil and gasapplications include high temperatures andpressures combined with high concentrationof dissolved solids, which make theenvironment especially corrosive. In someapplications, there will be significant levels ofacid gases, such as H2S and CO2, which affectsthe more common downhole materials.

BY: ROBERT HOUSER — ATI Wah Chang

The Nesjavellir Geothermal Power Plant in Iceland

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7OUTLOOK FOURTH QUARTER 2009

rgy Applications

titanium does not require corrosion inhibitorsfor production environments containing H2Sand high levels of CO2.

Mechanical PropertiesThe strength of titanium will depend on itsalloying elements. Table 1 summarizes severaltitanium alloys and other metals forcomparison.

With increased strength comes reducedformability; however manufacturers continueto search for an alloy with high strength,

from commercially pure (Ti Grades 1-4) toalloys with multiple alloying elements such asTi Grade 32 (Ti-5Al-1Sn-1Zr-1V-0.8Mo-0.1Si).

Titanium alloys are also attractive becausetheir density is 60%of that of steel. Theweight savings with higher strength materialsmeans increased load carrying capacity aswell as decreased wall thickness and sectionsize. With proper heat treatment, sufficientyield strengths have been obtained for risersand swivel components for offshore systems.Additional savings are achieved because

Ti Grade 7, which is suitable for this demandingenvironment, is Ti Grade 2 with the simpleaddition of PMG (palladium). The expectedlifetime of this alloy is over 10,000 yearsbecause stress corrosion cracking, localizedcorrosion and microbiological influencedcorrosion are not expected to occur[3].

Wave/TidalAlthough this form of power production isnot very widespread, it is another idealapplication for titanium. Titanium has beenwidely studied for its corrosion resistance inseawater. There are even boat hulls made oftitanium. It won’t be long before you hearabout power buoys off the Pacific coastlinebeing installed with corrosion resistant metals.

TITANIUM CHARACTERISTICSASTM has registered 38 grades of titanium;however, only a few are commonly used inindustry. Their strength to weight ratio makestitanium alloys ideal for aerospace applicationsas well as offshore heat exchangers. Theirthermal conductivity is 30% greater than 300series stainless steel. Titanium grades range

[ continued on page 8 ]

Comparison of Corrosion Resistant Alloys

Table 1.

Alloy Ultimate, ksi Yield (0.2%) ksi Elongation %

Ti Gr2 50 40 20

Ti Gr5 130 120 10

Ti Gr7 50 40 20

Ti Gr9 90 70 15

Ti Gr12 70 50 18

316 SS 85 30 40

Nickel Alloy 625 115 60 30

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8 FOURTH QUARTER 2009 OUTLOOK

Titanium for RenewaTitanium for Renewable Energy Applications[ continued from page 7]

Copyright ©2009 Wah Chang. All rights reserved.Reproduction of this newsletter by any means, in wholeor in part, without written permission is prohibited bylaw. Outlook is published quarterly by Wah Chang. Thenewsletter contains information on reactive and refractorymetals, including hafnium, niobium, titanium, vanadiumand zirconium, as well as chemicals. The properties listedherein are average values based on laboratory and fieldtest data from a number of sources. They are indicativeonly of the results obtained in such tests and should notbe considered as guaranteed maximums or minimums.The starburst logo and Wah Chang are registeredtrademarks of ATI Properties, Inc.

Layout by designpointinc.com

President .............................................. John Sims

Vice President – Commercial... Parry Walborn

Director of Sales ........................... Gary Kneisel

Editor ........................................... Kirk Richardson

INFORMATION & ORDER CONTACTS

ATI Wah Chang – HeadquartersPO Box 460Albany, Oregon 97321T 541.926.4211F 541.967.6990www.wahchang.comwww.corrosionsolutions.comwww.wahchanglabs.com

Sales/Tech SupportT 541.967.6977F 541.967.6994custserv@wahchang.com

CPI Service Center – UST 541.917.6739F 541.924.6882ellen.baumgartner@wahchang.com

INFORMATION ONAGENTS/DISTRIBUTORS

CPI ProductsT 541.967.6906

Nuclear-Grade AlloysT 541.967.6914

Ti, V, and Nb ProductsT 541.967.6977

AFFILIATED COMPANIES

ATI AllvacT 704.289.4511www.allvac.com

ATI Allegheny LudlumT 800.258.3586www.alleghenyludlum.com

ATI Engineered ProductsT 615.641.4200www.metalworkingproducts.com

Copyright ©2010 ATI Wah Chang. All rights reserved.

Reproduction of this newsletter by any means, in whole

or in part, without written permission is prohibited by

law. Outlook is published quarterly by ATI Wah Chang.

The newsletter contains information on reactive and

refractory metals, including hafnium, niobium, titanium,

vanadium and zirconium, as well as chemicals. The

properties listed herein are average values based on

laboratory and field test data from a number of sources.

They are indicative only of the results obtained in such

tests and should not be considered as guaranteed

maximums or minimums. The starburst logo and ATI Wah

Chang are registered trademarks of ATI Properties, Inc.

Layout by designpointinc.com

President .............................................. John Sims

Vice President – Commercial... Parry Walborn

Editor ........................................... Kirk Richardson

INFORMATION & ORDER CONTACTS

ATI Wah Chang – HeadquartersPO Box 460Albany, Oregon 97321T 541.926.4211www.wahchang.comwww.corrosionsolutions.comwww.wahchanglabs.com

Sales/Tech SupportT 541.967.6977F 541.967.6994custserv@wahchang.com

CPI Service Center – UST 541.917.6739F 541.924.6882ellen.baumgartner@wahchang.com

INFORMATION ONAGENTS/DISTRIBUTORS

CPI ProductsT 541.967.6906

Nuclear-Grade AlloysT 541.967.6914

Ti, V, and Nb ProductsT 541.967.6977

AFFILIATED COMPANIES

ATI AllvacT 704.289.4511www.allvac.com

ATI Allegheny LudlumT 800.258.3586www.alleghenyludlum.com

ATI Engineered ProductsT 615.641.4200www.metalworkingproducts.com

formability and weldability. One such alloy isTi Grade 38, which is slightly less strong (115ksi) than Ti Grade 5, but readily formablewhen cold and weldable[4].

All of the materials shown in Table 1 arereadily available in cast, forged blocks, bars,sheet, plate, and tubes. One exception is TiGrade 5, a material so inherently strong thatit cracks when fabricated into tubes. Anyheavy forming requires working this materialat elevated temperatures.

Corrosion ResistanceTitanium exhibits excellent corrosion resistancein oxidizing chloride environments, which ledto some of its first applications in the chemicalprocess industry over 30 years ago. Thecorrosion resistance of titanium relies on theformation of a thin oxide film, which occursspontaneously in air or water. Once the oxidefilm is compromised, damage may occur.

Reducing acids are often the cause ofgeneral corrosion on titanium. The corrosion

resistance of titanium in reducing acids(hydrochloric, sulfuric, phosphoric, etc.) willdepend on concentration and temperature.

When Ti Grade 2 will not work becauseof concentration or temperature concerns,other titanium alloy grades, like Ti Grade 12,may be viable alternatives[5]. There are otherlimitations that can cause problems withtitanium, such as crevice corrosion. AlthoughTi Grade 5 and Ti Grade 2 can suffer crevicecorrosion in high temperature hypersalinebrines, no crevice attack occurred on Ti Grade2 when low to medium (< 15,500 ppm)chloride brines were tested[6]. Titanium alloyscontaining aluminum, tin, manganese, cobaltand or oxygen greater than 0.317 percentare susceptible to stress corrosion crackingcaused by chloride ions concentrating in pre-existing cracks[7].

Another alternative to increase titanium’s

corrosion resistance is to add small amountsof a PGM, typically palladium or ruthenium.The PGM addition has no effect onmechanical properties, but enhances thecorrosion resistance of the material inchlorides and extends the range ofperformance in mildly reducing environments.A common use of these grades is for gasketfaces and crevices where Ti Grade 2 mightbe subject to crevice corrosion or pittingunder NaCl deposits[8].

For more information about alloys forrenewable energy applications, contact ATIWah Chang at 541-967-6977. a

REFERENCES1. Ellis, P., Smith, C., Keeney, R., Kirk, D., Conover,

M., and Radian Corporation: “CorrosionReference for Geothermal Downhole MaterialsSelection”, Contract No. DE-AC03-81SF11503,(1983), 7, 101.

2. Sanyal, S.: “Future of Geothermal Energy”,Proceedings, CanGEA Conference, Vancouver,B.C., Canada (2009).

3. Hua, F., Mon, K., Pasupathi, P., Gordon, G.,and Shoesmith, D.: “Corrosion of Ti Grade 7and Other Ti Alloys in Nuclear Waste RepositoryEnvironments – A Review”, Proceedings,Corrosion 2004, NACE International, PaperNo. 04689.

4. Kerr, J., Stoiber, R., and Hebda, J.: “NewApplications for 425”, Proceedings, CorrosionSolutions Conference, Sunriver, OR (2005).

5. Schutz, R., and Grauman, J.: “Selection ofTitanium Alloys for Concentrated Seawater,NaCl and MgCl2 Brines”, Proceedings, SanFrancisco, CA (1986).

6. Thomas, R.: “Titanium in the GeothermalIndustry”, GHC Bulletin (December, 2003),22-26.

7. Ellis, P.: “Geothermal Materials Survey:Arkansas Power and Light Development andDemonstration Project. 100KW Power SystemUsing Direct Contact Heat Exchangers, ElDorado, Arkansas”, Radian Corporation, July1980, Contract No. AC02-79ET27026, (1980),5, 16, 20.

8. Blauvelt, P., Rowan, D., Motiva Enterprises LLC,Willey, B., McMaster, J., and TitaniumFabrication Corporation: “Titanium – ProvenPerformance in Hydrocarbon Processing”,Proceedings, Corrosion 2000, NACEInternational, Paper No. 00684.

Titanium exhibits excellentcorrosion resistance in oxidizingchloride environments...