1、Designation:C70372(Reapproved 2016)Standard Test Methods forSpalling Resistance of Porcelain Enameled Aluminum1This standard is issued under the fixed designation C703;the number immediately following the designation indicates the year oforiginal adoption or,in the case of revision,the year of last
2、revision.A number in parentheses indicates the year of last reapproval.Asuperscript epsilon()indicates an editorial change since the last revision or reapproval.INTRODUCTIONThis test,using an ammonium chloride or antimony trichloride test solution,covers an acceleratedprocedure for determining the r
3、esistance of porcelain enamel coatings on aluminum and aluminumalloys to spontaneous loss of adhesion(spalling)resulting from exposure to moisture,weathering,orother environmental stress.1.Scope1.1 These test methods cover accelerated determination ofthe resistance of porcelain enamel coatings on al
4、uminum alloysto spalling from exposure to moisture or weathering.TestMethod A,2using a 5%solution of ammonium chloride,requires 96-h immersion while Test Method B,3using a 1%solution of antimony trichloride,is completed after 20 h ofimmersion.The spalling tendency is evaluated by the samecriteria in
5、 both methods.While either method is suitable formagnesium silicon alloys,such as 6061,Test Method B ispreferred for simple alloys or commercially pure aluminum,such as 1100.1.2 The test methods appear in the following order:SectionsTest Method AAmmonium Chloride4 9Test Method BAntimony Trichloride1
6、0 152.Terminology2.1 Definitions:2.1.1 spallinga defect characterized by separation of theporcelain enamel from the aluminum base metal withoutapparent external cause.Spalling can result from the use ofimproper alloys or enamel formulations,incorrect pretreatmentof the base metal,or faulty applicati
7、on and firing procedures.3.Significance and Use3.1 It is difficult to overemphasize the importance of thespall test.Porcelain enameled aluminum that fails this test willprobably spall in service if subjected to moisture or weather-ing.TEST METHOD AAMMONIUM CHLORIDE4.Apparatus4.1 Container,glass or p
8、lastic,large enough to immerse thetest area of the specimen completely and hold a minimum of 3mL of solution per square centimetre of the immersed surface.No metal other than the base metal of the specimen may beexposed to the test solution.5.Reagent5.1 Ammonium Chloride Solution(5%)The test solutio
9、n,freshly prepared,shall consist of 5 parts,by mass,of ammo-nium chloride(NH4Cl)(technical grade is adequate)dissolvedin 95 parts,by mass,of water.Deionized or distilled water ispreferred,but in the case of very large production pieces,tapwater may be used.Sufficient solution shall be prepared toper
10、mit complete immersion of the specimens.6.Test Specimens6.1 Full-size production pieces should be tested.When thisis not practical,specimens approximately 4 by 6 in.(102 by152 mm),cut from production parts should be tested.At leastone representative specimen from each“job”or each 1000 ft2(93 m2)of p
11、roduction,whichever is applicable,should be spalltested.Spall-tested pieces should not be shipped.6.2 Test production parts in as-produced condition.7.Procedure7.1 Immerse the test specimens completely in the NH4Clsolution at room temperature.Large production pieces may be1These test methods are und
12、er the jurisdiction of ASTM Committee B08 onMetallic and Inorganic Coatings and are the direct responsibility of SubcommitteeB08.12 on Materials for Porcelain Enamel and Ceramic-Metal Systems.Current edition approved Nov.1,2016.Published November 2016.Originallyapproved in 1972.Last previous edition
13、 approved in 2011 as C703 72(2011).DOI:10.1520/C0703-72R16.2Method A is based on Bulletin AL-1a,Recommended Test Methods forEvaluation and Control of Quality of Porcelain Enamel on Aluminum,of thePorcelain Enamel Institute.3Method B is based on Bulletin T-51,Antimony Trichloride Spall Test ofPorcela
14、in Enameled Aluminum,of the Porcelain Enamel Institute.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 immersed in a container made by lining a packing box withpolyethylene plastic sheeting.7.2 Make a visual inspection after 96 h of immer
15、sion.NOTE1Variations of this test may be used for studies of processingvariables.These include scored or deformed samples,24 h inspection,andmultiple cycles of 96 h each.8.Evaluation8.1 Any of the following types of spall that develop within96 h shall constitute failure:8.1.1 Any spall area(revealin
16、g bare metal)extending18in.(3 mm),or more,in from an edge and more than 1 in.(25 mm)in length,8.1.2 Any spall area on the interior surface(not touching anedge)that is more than18in.(3 mm)to its maximumdimension,or8.1.3 More than six visible spall spots per 1 ft2(929 cm2)onthe interior surface.9.Report9.1 The report shall include the following:9.1.1 Evaluation of the specimen as passing or failing theimmersion test in 96 h,9.1.2 Complete identification of the specimen,including thebasis metal,met