Braham, V. J.

Christenson, B.W.

Engelberg, D.

Ikeuchi, J.

Kurata, J.

Lichti, K. L.

Nanjo, H.

Sanada, N.

English

Volcanic hot pools on White Island, New Zealand provide ready access to acidic fluids at atmospheric pressure. These hot pools can be used to study the corrosion properties of construction materials that might be used for energy production from deep-seated and magma-ambient geothermal systems, or from shallow resources producing acidic fluids. corrosion results for a 1,hot pool are presented. A select group of moderate and high alloy materials appear suitable for energy plant applications. Chemistry and corrosion mechanism models provide some reasons for the experimental observations. Corrosion control experiments in fluids removed from the hot pool demonstrated that a decrease in the instantaneous corrosion rate of carbon steel can be achievedby adjustment

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The University of Manchester ResearchCorrosion Properties of a Volcanic Hot SpringLink to publication record in Manchester Research ExplorerCitation for published version (APA):Engelberg, D., Lichti, K. L., Braham, V. J., Sanada, N., Kurata, J., Nanjo, H., Ikeuchi, J., & Christenson, B. W.(1998). Corrosion Properties of a Volcanic Hot Spring. In PROCEEDINGS OF THE NEW ZEALANDGEOTHERMAL WORKSHOP (pp. 97-102). University of Auckland, Geothermal Institute.Published in:PROCEEDINGS OF THE NEW ZEALAND GEOTHERMAL WORKSHOPCiting this paperPlease note that where the full-text provided on Manchester Research Explorer is the Author Accepted Manuscriptor Proof version this may differ from the final Published version. If citing, it is advised that you check and use thepublisher's definitive version.General rightsCopyright and moral rights for the publications made accessible in the Research Explorer are retained by theauthors and/or other copyright owners and it is a condition of accessing publications that users recognise andabide by the legal requirements associated with these rights.Takedown policyIf you believe that this document breaches copyright please refer to the University of Manchester’s TakedownProcedures [http://man.ac.uk/04Y6Bo] or contact uml.scholarlycommunications@manchester.ac.uk providingrelevant details, so we can investigate your claim.Download date:09. Jun. 2022Proceedings 20th NZ Geothermal Workshop 1998CORROSION PROPERTIES OF A VOLCANIC HOT SPRINGK.A. V.J. D. N.J. B.W.PerformanceTechnologiesLtd., Lower Hutt,National Industrial Research Institute, AIST, MITI, Sendai, Japanof Geological Nuclear SciencesLtd., Taupo,SUMMARY - Volcanic hot pools onWhite Island, New Zealand provide ready access to acidic fluids atatmospheric pressure. These hot pools can be used to study the corrosion properties of constructionmaterials that might be used for energy production from deep-seated and magma-ambient geothermalsystems, or from shallow resources producing acidic fluids. corrosion results for a 1,hotpool are presented. A select group of moderate and high alloy materials appear suitable for energy plantapplications. Chemistry and corrosion mechanism models provide some reasons for the experimentalobservations. Corrosion control experiments in fluids removed from the hot pool demonstrated that adecrease in the instantaneouscorrosion rate of carbon steel can be achievedby adjustment.1. INTRODUCTIONDeep geothermal resources, located belowconventional shallow reservoirs, offerdevelopers the opportunity to increaseproduction capacity or field by tappinghigher temperature fluids from areas feeding theshallower reservoirs. These fluids are ofrelatively low and consequently have highercorrosivity (Sanada et al, 1997). Geothermalwells cased with materials suitable for long termproduction of aggressive acidic fluids are rare.The work reported here was initiated in 1993and is part of an effort to use natural volcanicenvironmentsto aid in the selection of materialsfor aggressive geothermal fluids (Kurata et al,1994, 1995, Lichti et al, 1996,tests conducted on White Islandinvolved the direct exposure of metal samples involcanic features, including hot pools whichprovide a similar chemistry to that of aggressivedeep well fluids, except that the hot pools are ata of 100°C and are at atmosphericpressure. Deep well fluids may havetemperatures in excess of 300°C and pressuresin excess of bar.Acidic geothermal wells are encountered inmany shallow resources and thechemistry and corrosivity of these systems havebeen partially explored (Sanada et al, 1995,1998, Lichti and Sanada, 1997, Lichti et al,Ikeuchi et al, 1982, 1997).Materials, process and plant options consideredby developers in their efforts to utilise thesemore aggressive fluids have been surveyed(Lichti and Sanada, 1997). Materialsexperience with deep wells, acid wellsencountered in shallow reserves and volcanicenvironments was used to assert the feasibility,potential costs and risk of development of acidicand deep geothermal resources, with the provisothat downhole corrosion control would berequired. The need for downhole corrosioncontrol has been further explored amodelling point of view (Ikeuchi et al, 1997,Lichti et al,The work reported here uses one of thesereadily available volcanic hot pools todetermine the corrosion behaviour of candidateand to explore options for downholecontrol.2. BACKGROUNDMaterials tests in White Island hot pools hadpreviously concentrated on a pool called BlackPot, a 99-100°C hot pool of 4. However, amore acidic hot spring area located next tofumarole Hot Pool became availablein 1997 (Lichti et al., Realisation of thecritical need for downhole corrosion control inthe development of deep and shallow acidicwells (Lichti and Sanada, 1997) promptedadditional studies of the corrosion properties ofPool at a temperature of 99-100°C and aof 1.4. Over the test period, Pool had acentral column of about 200high. The water contained fine silty suspendedmaterial that was off-white in colour. The pooldepth was approximately 200 and the pooldiameter was approximately 1 m. Digging ofthe pool to give greater depth resulted in morevigorous discharge from numerous points in thebottom of the pool. Disturbing sulfur depositsby digging the edge of the pool resulted in agreen film on top of the pool.Damming of the low side was a viable means of97increasing pool depth without causing excessdamage to the tourist-type environment.Previous experimental work concluded that(Kurata et al, Lichti et al,passive films or scales formed on metalcoupons exposed in Black Pot and slowedcorrosion to low levels although loweralloy materials were subject to pittingcorrosionhigh unacceptable corrosion rates wereobserved in Pool for all the materialstested; carbon steel, 12% Cr stainless steel,Types 304 and 316 stainless steels.3. EXPERIMENT RESULTSThis work concentrated on measuring thecorrosivity of Pool including (Figure 1):000000instantaneous corrosion rate measurementsusing the Linear Polarisation Resistance(LPR) technique on selected low and highalloy materials either directly exposed inthe pool or in water removed from the pool(Lichti and Wilson (1980) provide adescription of the LPR corrosion ratetechnique applied to g e o t h e d fluids)corrosion potential measurements ofselected metals and alloys (including Pt forredox potential determination) and Cr-Platevs or referenceelectrodes either in the pool or in waterremoved the pool (reported as vsStandardHydrogen Electrode, SHE)in-situ measurements with a single1) calibration solution of 0.1 N at ornear the pool temperaturetrials on the effect of adjustment, fiom1.6 to 6 on the instantaneous LPR corrosionrate of carbon steel in water removed fiomthe pool and in mixed acid (0.1 M0.05 M solution in the laboratorycoupon exposuresof low alloy materials for4 hours in the hot poolcoupon exposures of high alloy materialsfor 43 days in the hot pool, the Teflon boxcontaining the coupons was filled with thefine silt throughout the experiment.sampling of the water and suspended solidsfor chemical analysis.The materials tested have been describedelsewhere (Lichti et al., The corrosionpotential and LPR measurements at times gavespurious results, which were not understood atthe time. Attempts to measure the LPR of theduplex alloy 2507, Alloy 33, Alloy andAlloy 28 occasionally failed due to exposedelectrodes having corrosion reactions.For example, in one experiment, 2507 had oneelectrode active = -185 and theothers passive =The short term (4 hour) exposure of couponmaterials, carbon steel, 12% Cr and Type 316Lstainless steel, give a benchmark of theof Pool towards these materialsCr-plate on carbon steel and substrates wastotally corrodedwithin minutes of exposure.The adjustment of was achieved byadditions of 1 M NaOH solution to fluidremoved the pool and held in a preheated,heavy wall, glass container. Instantaneouscorrosionrates for carbon steel were obtained asa function of A series of experiments wasrequired to complete the measurements as thetemperature of the solutions rapidly dropped.The temperature range used was 80 toChange of from 1.5 to 6.0 gave a roughlylinear decrease in corrosion rate of carbon steelfiom 31.9 to 0.8 (Table 1).Table 1- Corrosion rate of carbon steel inadjusted water fiom Pool and laboratorysolution (both solutions were naturally aerated).Pool Water .T CR T1.52 77 31.9 1.10 95 47.42.26 71 23.3 2.00 95 37.13.28 80 11.5 3.25 95 31.7, 4.19 68 6.175 4.7 5.00 95 8.95.97 60 0.84.The corrosion chemistry of hot poolsencountered in natural volcanic features varies,from near neutral or alkali pH-chloride typewaters, to waters that aremore aggressive to metals and alloys. Poolwas chosen for testing because of thetemperature and acidity, as reported in Table 2.The vigorous discharge of gas through the poolresults in the water having a high suspendedload. studies of this suspension showsthat it consists of abundant alunite, elementalsulfur and amorphous silica (opal withlesser quantities of pyrite.REACT (Bethke, 1992) was used to model thespeciation of dissolved constituents in the poolat the measured temperature of 100 "C. Sinceconcentrations in the water (Table 2) werebelow the detection level, the presence ofelemental sulfur in the pool was used toconstrain the redox state of the fluid via98I I I I I II1III IIIIIIIIIIIIIIIIIII99Table 2- Geochemistry of Hot Pool used for corrosiontestingonWhite Island, New Zealand.Location Date! T K Nn K Cn Mg SO, BIsland12.2.96 99 1.03 0.34 105 51 394 228 3,474 0.97 456 0.81 782 103.. .99 40 1.45 1.40 0.18 142 13.6 370 183 1,742 1.2 418 0.28 430 12229.7.98 99 57 1.59 1.44 0.17 142 15.5 304 183 1,576 3,360 1.0 406 0.24 430 122Table 3- High temperature chemistry of HotPool onWhite Island.Pool 12/2/96 Pool 16/6/98T c 100Pressure 1.013bara 1.013bara-47.800 -48.376Eh 208.81.5493320. 1873Na+Li+S04-101.0448.0359.0339.6361.9145.32.95248.8872.5611,0103.587708.9146.2220.389.593.5891.75343.14121E421E-07139.6414.8382.8333.1332.9101.47.21313.22108.00.28623,434415.735.363.230.17830.634517.8962.82 9.454Componentspresent at not shown.Mineral SaturationStates (logPyrite= 2.41, Quartz = 0.90, = 0.76, Chalcedony=0.49, Christobalite (alpha) = 0.49, 0.24,Christobalite(beta)= 0.18, Si02 (amorphous) 0.01, Sulfurequilibrium. This approach results in goodagreement between observed mineralogy andthe calculated saturation indices (Table 3). Thecalculated of the pool at 100 was 1.55 ata redox potential (Eh) of 210 whichcorrelates well with the measured parameters(compare Table 3 and Figure 1).5. POTENTIAL-pH MODELSThermodynamic potential-pH diagrams(Figures 2 to 5) were prepared for the calculatedcorrosion chemistry (Table 3) and the primaryalloy elements of the iron-containing materialstested, using data fiom Cobble et al. (1982).The estimated corrosion potential ranges in thediagrams were based on the measured results(Figure 1).6. DISCUSSIONThe instantaneous LPR measurements madeafter only a few minutes of exposure (Figure 1)gave corrosion rate results which were similarto those obtained from weight loss experimentsfor the low alloy materials (4 hours exposure),but were higher than the corrosion ratesobserved on the high alloy materials (43 daysexposure). These differences suggest that, thelow alloy materials did not passivate in 4 hourswhereas the moderate to high alloy materialstook some time to passivate and may exhibitvariable performance. The coupons packed insilt could have benefited from the additionalshielding of the surface fiom the turbulentfluids.Both the coupon exposures and theinstantaneous LPR results provide acomparative measure of long term performance,although intermediate alloy materials may bemisrepresentedby LPR results. Nevertheless, itis useful to compare corrosion rate results andpotential measurements of the principal alloytypes tested at 1.5 (see Figure 1):000000000carbon steel (1007) corrosion rates are toohigh for common engineering applications12% Cr (410) stainless steel corrosion rateswere higher than carbon steel, suggestingthat alloying with Cr alone will not givesufficient corrosionresistanceaustenitic stainless steels and low Mocontent nickel-base alloys were readilycorroded 825, Alloy 28,Alloy 33, Alloythe two duplex stainless steels (2205 and2507) showed performance whichis attributable to rapid passivation of thehigher alloy material as indicatedby the corrosionpotential measurementscorrosion rates for the high alloy,base alloys and the cobalt alloy appear tobe directly dependent on Mo content andinversely dependentonFe contentand Cr-plate readily corroded, but Mogave a low corrosion rateand titanium alloys gave lowcorrosionratesthe corrosion potentials obtained for Pt(which give a measure of redox potential,Eh) in the pool, suggest that, in theundisturbed state, the water chemistry isindeed controlledby the S chemistry, whilein removed waters and in turbulent waters,air is readily entrained and the Eh raisesPitting Resistance Equivalent did notcorrelate with the occurrence of localisedcorrosioninitiation or penetration.-Iron-Sulfur-Water0ttiaI0ItV-1lteI IMolybdenum-Sulfur-WaterT =Total S =Adjustment of to 6 by addition of NaOHdecreased the instantaneous corrosion rate fiom31.9 to 0.8 Under long termaerated conditions, in static and turbulentenvironments, down to 3 or 4, passive filmswould be expected to and the corrosionrate would decrease to lower levels (Sanada etal, 1998). The work in the laboratory hasprogressed to simulation of the fieldenvironments under aerated conditions, with aresult In-plant field trials andaeratedpressure vessel tests of adjustment asa means of corrosion control are planned.E -2ICr IFigure 3 - Potential-pH diagram for- Ni IIIFigure 5 - Potential-pH diagram forHot Pool at T = 100°C000The Potential-pH (Pourbaix) diagram models ofcorrosion product stability for Fe, Ni, Cr andMo provide some additional explanation for theobservedperformance:Figure 2 shows the corrosion potential forFe at 1.5 is in the region of thediagram - active corrosion would bepredicted, as observedthe redox potential of the solution (asmeasured on the Pt metal sample) was 220and is in the middle of the S region ofstability, which is consistent with themethod of calculation of the chemistry andthe observedpresence of fiee S in the poolFigures 3 and 4 imply that pure Cr and Niwill corrode in these lowsolutions and this is consistent with theexperimental results for Ni, Cr-plate and,Ni-Cr-Fe (low Mo) alloysFigure 5 shows a large stability area forwhich is nearly independent ofand the results of Figure 1 indicate alloyingwith Mo is a key parameter in controllingcorrosion, but the presence of sulfides oroxides of molybdenum has not beenexperimentallyor analytically-101The low corrosion rate of the 2507 duplex alloyand stainless steel are anomalous inregard to their alloy content and consequently,their calls for furtherStainless steels and nickel-base alloys obtaintheir corrosion resistance through formation ofthin oxide films. In acid solutions thesefilms can break-down or be dissolved resultingin general corrosion at potentials approachingthat of carbon steel. Thesurface is said to be “active”. If the oxide filmstable and is not dissolved then thesurface is said to be in a “passive” state whichoccurs at a more positive potential. The rangeof potentials shown in Figure 1 for the stainlesssteels, and the observed variable performance ofthese alloys, indicates that mixedbehaviour is occurring.7. CONCLUSIONSVolcanic hot pools can be used to test materialsin acidic geothermal fluids at atmosphericpressure. Corrosion tests of candidateconstructionmaterials have been done in a 1hot pool on White Island, as a necessary step inthe development of deep and acidic g e o t h e dresources. A select group of alloys; duplexalloy 2507, austenitic stainless steeland nickel-base alloys 625, C276 and 59, acobalt alloy pure Mo, Ti and Ti alloysexhibited low corrosion rates. The goodof these alloys is attributed to theformation of passive films in the acidicenvironments. These filmshave yet to be fullycharacterised. Adjustment of by addition ofNaOH solution gives a reduction in corrosionrate of carbon steel, but long term tests arerequired to demonstrate the feasibility of thismethod of corrosion control for deep and acidicgeothermal wells.8. ACKNOWLEDGEMENTSThis paper was prepared using financial supportthe New Zealand Foundation for ResearchScience and Technology and fromAIST,MITI,Japan. The authors express their thanks to JR Buttle for permission to conduct the work onIsland.9. REFERENCESCobble, J.W., Murray, R.C. Jr., Turner, P.J. andChen, K. (1982). High-temperature thermodynamicdata for species in aqueous solution. NP-2400,Research Project 1167-1,Final Report to EPRI.Bethke, C. (1992) The geochemist’s workbench; auser’s guide to Rxn, Tact and Gtplot. Univ213Ikeuchi, J., Sanada, N., Asano, O., Kurata, Y.,Odawara, 0. and Okahara, Y . (1982). Corrosion anderosion-corrosion of iron-base alloys in ageothermal resource area (Onikobe) in Japan. ProcInt Conf on Geothermal Energy, Florence, Italy, ppIkeuchi, J., S., Kurata,Y., Pestov, 1. andSanada, N. (1997). Material damage in deepgeothermal well-bores. Proceedings 19th NZ GeoWorkshop, pp 175-180.Kurata,Y., Sanada, N. Nanjo, H., Ikeuchi, J. andLichti, K.A. (1994). Field testing of materials atWhite Island. Workshop on Deep-seated andMagma-Ambient Geothermal Systems, Tsukuba,Japan, Mar, 167-170.Kurata,Y.,Sanada, N. Nanjo, H., Ikeuchi, J. andLichti, K.A. Material damage in a volcanicenvironment. Milan, Italy, May, 2409-2414.Kurata,Y., Sanada, N. Nanjo, H. and Ikeuchi, J.(1 Casingpipe materialsfor deep geothermalwells.GRCTrans,Vol 19, pp 105-109.Lichti, K.A. and Wilson, P.T. (1980). Thedetermination of metal corrosion rates in geothermalcondensate using electrochemical techniques. Proc3rd NZ Geothermal Workshop, pp 37-42.Lichti, K.A., Gilman, N.A., Sanada, N., Kurata,Y.,Nanjo, H., Ikeuchi, J. and Christenson, B.W. (1996).Corrosionchemistry of some volcanic environments.Proc 18thNZ Geothermal Workshop, pp 21-28.Lichti, K. A. and Sanada,N. (1997). Materials issuesfor utilisation of deep geothermal systems,Proc 19thNZ Geothermal Workshop, pp 169-174.Lichti, K.A., Swann,S.S., S.P., Sanada, N.,Kurata,Y., Nanjo, H., Ikeuchi, J. and Christenson,, B.W. Corrosion in volcanic gases. in ProcNEDO Int Geo Symp, Mar 1 Sendai, Japan,NEDO, 154-163.Lichti, K.A., Swann, S.S., Sanada, N., Kurata, Y.,Nanjo, H., Ikeuchi, J. and Christenson, B.W.Corrosion in volcanic hot springs. GRC, 299-307.Lichti, K.A., White, S.P., Sanada, N.Corrosion in deep and acidic geothermal wells.PNOC-EDC Geo Manila,Lichti, K.A., White, S.P., Sanada, N.Modelling of acid fluid wellbore chemistry andimplicationsfor utilisation.Proc NZ GeothermalWorkshop.Sanada, N., Kurata, Y., Nanjo, H. and Ikeuchi, J.(1995) Material damage in high velocityfluids.GRC19, 359-363.Sanada, N., Kurata, Y. and Lichti, K.A. (1997).Evaluation and development of Deep Geothermalresources - Materials Subtask of researchCollaboration GRCTrans, 1,pp 317-324.Sanada, N., Kurata,Y., Nanjo, H., Ikeuchi, J. andS. (1998). Corrosion in acidic geothermalflows with high velocity. NZ GeothermalWorkshop.--i102

Corrosion Properties of a Volcanic Hot Spring

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Corrosion Properties of a Volcanic Hot Spring

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