ABSTRACT
Bipolarspray-chargingstrategieshaveearlierbeeninvestigatedbyCooperandLaw[4]to ameliorateanothertarget-imposedproblemlimitingelectrodeposition-namely,thedeleterious electricdischargesinducedbyexcessivespace-chargefieldstoflowfromsharpedgesandtips (e.g.,plantleaftips)ofgrounded,conductivetargets.Alternating(e.g.,2-36Hz)thedropletchargepolaritycarriedonsuccessivespray-cloudsectorstravelingthroughthenozzle-to-target regionwasexperimentallyshowntosignificantlydiminishthespraycloud'soverallspace-charge electricfieldwhilestillmaintaining,toadegree,localdepositionfieldsandbeneficialcharge transfers(Fig.1)atinternalandexternaltargetsurfaces.Forthispresentworkitwas hypothesizedthatexcessivesurface-chargebuildupsonnonconductiveandelectricallyisolated targetsundergoingelectrostaticcoatingcouldlikewisebecontrolledbyappropriatebipolarspraycharging.Theobjectiveofthispaperistoexperimentallyquantifyspraydepositionasafunction ofbipolarspraychargingfrequency(viz.,sevenvaluesoverthedc-4Hzrange),andcompare resultswithsimilarlyappliedunchargedspray,forthefollowingelectricallydifferingtarget conditions:a)groundedconductivetarget;b)electricallyisolatedconductivetarget;c) nonconductivetarget;andd)nonconductivetargetsurfaceoverlyinggroundedsubstrate.
