ASTM_D_5682_-_95.pdf

Designation:D 5682 95Standard Test Methods forElectrical Resistivity of Liquid Paint and Related Materials1This standard is issued under the fixed designation D 5682;the number immediately following the designation indicates the year oforiginal adoption or,in the case of revision,the year of last revision.A number in parentheses indicates the year of last reapproval.Asuperscript epsilon(e)indicates an editorial change since the last revision or reapproval.1.Scope1.1 These test methods cover the determination of specificresistance(resistivity)of liquid paints,solvents,and otherfluids in the range of 0.6 to 2640 MV-cm.1.2 Test Method A describes a procedure for making resis-tance tests with a commonly used paint application2testassembly(Fig.1).1.3 Test Method B describes a procedure for making resis-tance tests with a conductivity meter3(Fig.2).1.4 This standard does not purport to address all of thesafety concerns,if any,associated with its use.It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2.Terminology2.1 Definitions:2.1.1 specific resistance(resistivity)The ratio of the d-cpotential gradient in volts per centimeter paralleling the currentflow within the specimen to the current density in amperes persquare centimeter at a given instant of time and underprescribed conditions.2.1.1.1 DiscussionThis is numerically equal to the resis-tance between opposite faces of a centimeter cube of the liquid.The units are ohm centimeters(or megohm centimeters).2.2 Definitions of Terms Specific to This Standard:2.2.1 kilohms(KV)resistance value equal to 1000 V(103).2.2.2 megohms(MV)resistance value equal to 1 000 000V(106).2.2.3 ohm-centimeters(or megohm-centimeters)unit ofspecific resistance(resistivity).3.Summary of Test Methods3.1 Test Methods A and B measure direct current throughconcentric cylinder electrodes immersed in a liquid paintspecimen.4.Significance and Use4.1 These tests are suitable for testing paints adjusted forcompatibility with various electrostatic spray coating applica-tions,and by their use,spray performance can be optimized.5.Interferences5.1 Contamination of the specimen is the most likely causeof error.Very small amounts of water,acids,or polar solventswill lower the resistance of high resistivity solvents and paints.5.2 High humidity is not known to interfere with the testitself but can lead to water pickup by the specimen.Forrepeatable results,tests should be made under the sameatmospheric conditions and specimens should be stored andhandled so as to keep water pickup to a minimum.5.3 Resistivity varies with temperature.A standard testtemperature of 25C is recommended.Other temperatures arepossible on agreement between the producer and the user.5.4 Electrification time must be the same for every test dueto ion migrations that cause current flow to decrease with time.Variations with time of electrification can result in appreciablevariation in the test results.5.5 Equipment outlined in Test Methods A and B apply1These test methods are under the jurisdiction ofASTM Committee D-1 on Paintand Related Coatings,Materials,and Applications and is the direct responsibility ofSubcommittee D01.24 on Physical Properties of Liquid Paints and Paint Materials.Current edition approved March 15,1995.Published May 1995.2Paint application test assembly such as the Ransburg 70408-00 Tester orequivalent may be obtained from ITW Ransburg Electrostatic Systems,P.O.Box913,Toledo,OH 43697-0913.3Conductivity meter such as the Byk-Gardner LC2 conductivity meter,Model1722/1710 or equivalent may be obtained from Byk-Gardner,Inc.,2435 LindenLane,Silver Spring,MD 20910.FIG.1 Paint Application Test Assembly1AMERICAN SOCIETY FOR TESTING AND MATERIALS100 Barr Harbor Dr.,West Conshohocken,PA 19428Reprinted from the Annual Book of ASTM Standards.Copyright ASTMdifferent test voltages(45 V and 15 V,respectively).Because ofthis,some variation in results may be expected.6.Apparatus6.1 Paint Application Test Assembly2designed to providemeasurement of the electrical resistance of paint formulationsfor all electrostatic applications.To provide greater accuracy inmeasuring low resistance paints,the meter is equipped withdual range selection.Range“A”is.005 to 1 MV,Range“B”is.05 to 20 MV.7.Reagents and Materials7.1 Low Resistivity Cell Constant Standards(see AppendixX1 for cell constant determination method).7.2 Potassium chloride,1000 V/cm.47.3 Cleaning Solvents and SolutionsIt is essential tothoroughly clean the probe before and after tests.The cleaningsolvent should be chosen on the basis of the paint tested.Duecare must be exercised in cleaning to ensure all cleaningsolvents are removed from the probe before reusing.The probemust be dry and free from contaminates or results will vary.TEST METHOD A8.Standardization8.1 For maximum accuracy,the probe should be standard-ized to determine the exact cell constant