ASTM_A_1071_-_A_1071M_-_11_2015.pdf

Designation:A1071/A1071M11(Reapproved 2015)Standard Test Method forEvaluating Hygrothermal Corrosion Resistance ofPermanent Magnet Alloys1This standard is issued under the fixed designation A1071/A1071M;the number immediately following the designation indicates theyear of original adoption or,in the case of revision,the year of last revision.A number in parentheses indicates the year of lastreapproval.A superscript epsilon()indicates an editorial change since the last revision or reapproval.1.Scope1.1 This test method covers the equipment,procedures,andmeasurement of the resistance of permanent magnet alloysagainst corrosion in high temperature,high pressure watervapor environments.This test is also known as the BulkCorrosion Test(BCT).1.2 The values and equations stated in customary(cgs-emuand inch-pound)units or SI units are to be regarded separatelyas standard.Within this standard the SI units,when differentfrom customary units,are shown in brackets,the values statedin each system may not be exact equivalents;therefore,eachsystem shall be used independently of the other.Combiningvalues from the two systems may result in nonconformancewith this standard.1.3 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.Referenced Documents2.1 ASTM Standards:2D3330/D3330M Test Method for PeelAdhesion of Pressure-Sensitive Tape2.2 JEDEC Standards:3JESD22-A102-C Accelerated Moisture Resistance Unbi-ased Autoclave3.Terminology3.1 Definitions:3.1.1 bulk corrosion test(BCT)grade,ngrade given toranges of specific weight loss to indicate the relative corrosionresistance of a material.(The grades are listed in 15.2.)3.1.2 specific weight loss,nweight loss of the specimenper unit of exposed surface area,in units of milligrams persquare centimetre,due to corrosion and disintegration.4.Summary of Test Method4.1 Permanent magnet samples are exposed to pressurizedsteam to determine the resistance of these materials,especiallyrare earth-type permanent magnets,to degradation by thecombined action of heat and water vapor.The resulting weightloss(including removed loosely-attached material)is used torate the hygrothermal corrosion resistance of the magnet.5.Significance and Use5.1 This test method provides a controlled corrosive envi-ronment which can be utilized to produce relative corrosionresistance information for sintered permanent magnets.5.2 Although prediction of performance in natural environ-ments has seldom been statistically correlated with corrosiontest results,sufficient empirical results are available to supportthe usefulness of this test in quantifying relative resistance tocorrosion from moisture and heat.5.3 The reproducibility of results in this test method isdependent on the type,size,and shape of specimens tested,andthe control of the operating variables.In any testing program,sufficient replicates should be included to establish confidencelimits.Replicates may be run simultaneously,in subsequenttest runs,or in duplicate test chambers.5.4 When multiple test chambers and operators are utilized,efforts shall be made to perform a suitable repeatability andreproducibility study for the equipment,operators,and testmethod.6.Interferences6.1 This test method will not yield meaningful results ifnonhomogeneous specimens such as assemblies or partiallycoated magnets are tested because of the potential aggravatingeffect of galvanic corrosion between dissimilar materials,1This test method is under the jurisdiction of ASTM Committee A06 onMagnetic Properties and is the direct responsibility of Subcommittee A06.01 on TestMethods.Current edition approved Oct.1,2015.Published October 2015.Originallyapproved in 2011.Last previous edition approved in 2011 as A1071/A1071M 11.DOI:10.1520/A1071_A1071M11R15.2For 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.3Available from JEDEC Solid State Technology Association,2500 WilsonBoulevard,Arlington,VA 222013834.www.jedec.orgCopyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 chemical reactivity with included materials,incompletely ex-posed surfaces,and difficulty in determining the amount ofweight loss attributable to the magnet and coating.6.2 Many cleansers contain bleach or chlorides which willincrease the corrosion rate of the samples being tested.Do notuse bleach-or chloride-containing cleansers to clean theinterior of the test chamber or sample racks.Nonmetallicscrubbing pads and water rinsing have been found to besuitable for routine cleaning of chambers and racks.7.Apparatus7.1 AutoclaveAheated pressure chamber capable of