ASTM_A_239_-_14.pdf

Designation:A23914Standard Practice forLocating the Thinnest Spot in a Zinc(Galvanized)Coatingon Iron or Steel Articles1,2This standard is issued under the fixed designation A239;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.This standard has been approved for use by agencies of the U.S.Department of Defense.1.Scope*1.1 This practice covers the procedure for locating,by theuse of a solution of copper sulfate,the thinnest spot in a zinccoating(hot dipped,electroplated,or sprayed)on iron or steelarticles that are coated after the shape is produced by casting,drawing,pressing,or other forming methods.Examples are:electrical metallic tubing and rigid conduit pipe,castings andforgings,and structural steel;on special hardware,such aspoleline,builders,and farm implement hardware;bolts,nuts,screws,and other miscellaneous general hardware.1.2 The use of this practice with zinc coating depositedthrough different processes(such as hot dipped,electroplated,or sprayed)requires caution in interpretation since the endpoint may vary considerably between different zinc-coatingsystems.1.3 Excluded from this practice is sheet steel from hot-dipor electrocoating lines as the sheet products are normallysubject to additional forming after the coating process.Alsoexcluded from this practice are all zinc-coated wire and wireproducts either continuously or batch coated before or afterforming.WarningPast research(dating from around 1963)has indicated that this practice can be influenced by operatortechnique.Variations can be due to the difference in handpressure used to wipe the sample or the inability of the operatorto recognize the end point.1.4 This technique removes the zinc coating on the surfaceof the part being examined.This coating removal makes thepart or article unusable after testing.This technique may not besuitable for parts fabricated into their final configuration,sincethey will not be acceptable after testing.1.5 The results of this practice should not be used to predictthe service life of the galvanized coating.Other factors such aslocation of the thinnest spot,orientation of the part in service,and specific environmental conditions will also affect theservice life.1.6 The values stated in inch-pound units are to be regardedas standard.The values given in parentheses are mathematicalconversions to SI units that are provided for information onlyand are not considered standard.1.7 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.Significance and Use2.1 This practice is designed to locate the thinnest portionsof the zinc coating on newly coated items(see Appendix X1).Variations in coating thickness can be due to the process bywhich the zinc is applied(hot dipped,electroplated,or sprayed)or by the geometry of the part that is coated.During hot-dipgalvanizing,the coating thickness is affected by the drainagepattern of the molten zinc,while during zinc spraying(metallizing),coating thickness can be dependent on theoperators manipulation of the spray nozzle.The geometry ofthe part can also influence coating thickness especially duringhot-dip galvanizing,where peaks and valleys on the part cancause molten zinc to build up or thin out.This practice isdesigned to identify those areas of the part where the coating isthin.3.Copper Sulfate Solution3.1 The copper sulfate solution shall be made by dissolvingapproximately 36 parts by weight of commercial cupric sulfatecrystals(CuSO45H2O)in 100 parts by weight of distilledwater(see 3.1.1).Heat may be used to complete the solution ofcupric sulfate crystals.If heated,the solution shall be allowedto cool.The solution shall then be agitated with an excess ofpowdered cupric hydroxide(Cu(OH)2),about 0.13 oz/gal(1.0g/L)of solution.The presence of an excess of cupric hydroxidewill be shown by the sediment of this reagent at the bottom of1This practice is under the jurisdiction of ASTM Committee A05 on Metallic-Coated Iron and Steel Productsand is the direct responsibility of SubcommitteeA05.07 on Methods of Testing.Current edition approved May 1,2014.Published May 2014.Originallyapproved in 1940.Last previous edition approved in 2009 as A239-95(2009)1.DOI:10.1520/A0239-14.2This practice is used to locate the thinnest spot only,and is not intended as a testfor coating weight.This practice is to be used only within the limits of Section 1,Scope.*A Summary of Changes section appears at the end of this standardCopyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 the ves