Abstract
Magnetite(Fe3O4) isoneofthemostcommonoxidesformingdepositsandparticulatephasesin
industrialhightemperaturewatercircuits.Itscolloidalcharacteristicsplayaprincipalroleinthe
mechanismofdepositformationandcanbeusedascontrollingfactorstopreventorminimizedeposit
formationanddamageofindustrialpipelinesduetounder-depositcorrosion.Inthisstudy,ahigh
temperatureparticleelectrophoresistechniquewasemployedtomeasurethezetapotentialatthe
magnetite/waterinterface—the parameterthatcontrolscolloidalstabilityofparticles,theiraggrega-
tion, anddeposition.Themeasurementsweremadeattemperaturesupto200 1C overawiderangeofpH.
The isoelectricpointsofmagnetite,atwhichthedepositionofparticlesisincreased,weredeterminedatpH
6.35, 6.00,5.25,and5.05fortemperatures25,100,150,and200 1C, respectively.Theobserved
temperaturedependenceofzetapotentialandtheisoelectricpHpointofmagnetitecanhelptoexplain
the extentofinteractionsbetweenthecolloidalparticlesandthesteelwallsurfacesunderhydro-
thermalconditions,andindicatemethodsforcontrollingandmitigatingoxidedepositioninhigh
temperaturewatercycles.