ASTM_B_826_-_09_2015.pdf

Designation:B82609(Reapproved 2015)Standard Test Method forMonitoring Atmospheric Corrosion Tests by ElectricalResistance Probes1This standard is issued under the fixed designation B826;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()indicates an editorial change since the last revision or reapproval.1.Scope1.1 This test method provides a means for monitoringcorrosivity of environmental tests that involve exposure tocorrosive gases.1.2 This test method uses a resistance monitor(RM)probefabricated from a chosen metal conductor,with one conductorsegment uncovered to permit exposure of the chosen metalconductor to the corrosive gas mixture and the second conduc-tor segment covered to protect the metal conductor of thissegment from direct attack by the corrosive gas mixture.Thecovered conductor segment provides a reference for evaluatingchanges in the uncovered segment.The ratio of the resistanceof the exposed segment to that of the covered segment providesa measure of the amount of metal conductor that has reactedwith the corrosive gas test environment to form poorly con-ducting corrosion product,thus providing a measure of testcorrosivity.1.3 Resistance monitoring is applicable to a broad range oftest conditions by selection of the appropriate metal conductorand initial metal thickness.1.4 This method is similar in intent to Test Methods B808.1.5 The values stated in SI units are to be regarded asstandard.No other units of measurement are included in thisstandard.1.6 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 become familiarwith all hazards including those identified in the appropriateMaterial Safety Data Sheet(MSDS)for this product/materialas provided by the manufacturer,to establish appropriatesafety and health practices,and determine the applicability ofregulatory limitations prior to use.2.Referenced Documents2.1 ASTM Standards:2B808 Test Method for Monitoring ofAtmospheric CorrosionChambers by Quartz Crystal MicrobalancesB810 Test Method for Calibration ofAtmospheric CorrosionTest Chambers by Change in Mass of Copper CouponsB827 Practice for Conducting Mixed Flowing Gas(MFG)Environmental TestsG96 Guide for Online Monitoring of Corrosion in PlantEquipment(Electrical and Electrochemical Methods)3.Summary of Test Method3.1 The corrosivity of an atmospheric corrosion test such asa mixed flowing gas(MFG)type test is measured by monitor-ing the loss in electrical conductivity of a metal element whosesurface corrodes to form poorly conducting corrosion product.This corrosion product consumes metal from a conduction pathcausing an increase in electrical resistance.The resistance ofthe degraded conduction path is compared with a similar pathwhose surface is covered to prevent corrosion.This compari-son resistance also provides a temperature correction reference.The ratio of the electrical resistance of the path exposed to thecorrosive gases to that of the covered path is monitored duringthe test and compared to an expected ratio-versus-time curve toestablish the relationship of the test corrosivity to expected testcorrosivity.Alternatively,the ratio-versus-time curve for agiven atmosphere can be compared with the behavior of othercorrosive atmospheres to evaluate the relative corrosivity of thevarious atmospheres.4.Significance and Use4.1 Corrosivity monitoring of test environments provides ameans to monitor an integrated value of test corrosivity whichcannot be evaluated from test parameters themselves,such astemperature,humidity,and gas concentration.As such themonitor value can be used for specification purposes such as1This test method is under the jurisdiction of ASTM Committee B02 onNonferrous Metals and Alloys and is the direct responsibility of SubcommitteeB02.11 on Electrical Contact Test Methods.Current edition approved May 1,2015.Published May 2015.Originallyapproved in 1997.Last previous edition approved in 2009 as B826 09.DOI:10.1520/B0826-09R15.2For referenced ASTM standards,visit the ASTM website,www.astm.org,orcontact ASTM Customer Service at serviceastm.org.For Annual Book of ASTMStandards volume information,refer to the standards Document Summary page onthe ASTM website.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 test validation.Electrical resistance monitoring of conductorsexposed to corrosive media is a well-established practice.3,4,5,64.2 The resistance method assumes uniform corrosion overthe entire surface of the exposed metal conductor segment.Local corrosion such as pitting,crevice,or grain boundarycorrosion may provide invalid estimates of test corrosivity.Marked changes in slope of the curve of electrical resistanceratio versus time may i