ASTM_C_448_-_88_2016.pdf

Designation:C44888(Reapproved 2016)Standard Test Methods forAbrasion Resistance of Porcelain Enamels1This standard is issued under the fixed designation C448;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.INTRODUCTIONThis test is a means of quantifying the abrasion resistance of porcelain enamels through steady-statesubsurface abrasive wear with stainless steel ball bearings.Achange in gloss or weight loss is reportedthat can,through further evaluation,be correlated to the service life of the enameled ware.1.Scope1.1 These test methods cover determination of the resistanceof porcelain enamels to surface abrasion and subsurfaceabrasion.1.2 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:2C346 Test Method for 45-deg Specular Gloss of CeramicMaterials3.Summary of Test Methods3.1 The first of the tests described herein is intended for thedetermination of the resistance to surface abrasion of porcelainenamels for which the unabraded 45 specular gloss is morethan 30 gloss units.It consists essentially of measuring thespecular gloss of the specimens before and after a specifiedabrasive treatment of the surface,and taking the percentage ofthe original specular gloss that is retained after treatment as thesurface abrasion index.3.2 The second test is intended for the determination of theresistance to surface abrasion of porcelain enamels for whichthe unabraded 45 specular gloss is 30 gloss units or less.Itconsists of determining the weight loss by a specified abrasivetreatment and multiplying this weight loss by an adjustmentfactor associated with each abrasive tester,lot of abrasive,andlot of calibrated plate glass standards used.The adjustedweight loss is taken as an index of resistance to surfaceabrasion.3.3 The third test is intended for the determination of theresistance of porcelain enamels to subsurface abrasion.Itconsists of determining the slope of the linear portion of theabrasion time-weight loss curve and multiplying by an adjust-ment factor associated with each abrasion tester,lot ofabrasive,and lot of calibrated plate glass standards used.Theadjusted slope is taken as an index of resistance to subsurfaceabrasion.4.Significance and Use4.1 When a porcelain enamel is first subjected to abrasion ofthe type involved in these tests,the rate of wear or attrition isrelatively low.As the enamel is subjected to continuedabrasion,the rate of wear increases until it reaches a steadyvalue.Thereafter,the rate of wear remains almost constantuntil the enamel is penetrated and the underlying ground coator metal exposed.The abrasion that occurs during the period ofincreasing rate-of-weight loss is defined as surface abrasionand results in reduced gloss and cleanability with high-glossenamels and a modification of color,appearance,or surfacetexture,or combination thereof with low-gloss enamels.Theabrasion that occurs during the period of steady rate-of-weightloss is defined as subsurface abrasion and results in thedestruction of the continuity of the coating.These two types ofabrasion are not necessarily proportional,and since it isdesirable to be able to determine the resistance of porcelainenamel to both types of abrasion,it is necessary to deal witheach one separately.5.Apparatus5.1 Balance,having a capacity of approximately 200 g andaccurate to 0.0001 g.1These test methods are under 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 1959.Last previous edition approved in 2011 as C448 88(2011).DOI:10.1520/C0448-88R16.2For 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 5.2 Alloy Balls3Rust-resisting alloy balls of the type usedfor bearings,532in.(4 mm)in diameter.About 4 lb(1.8 kg)arerequired.Second-grade balls are satisfactory.5.3 Apparatus for Measuring Specular Gloss,4conformingto the requirements of Test Method C346 and having arepeatable precision of not less than 60.5 gloss unit.Meansshall be provided for positioning the specimen,with respect tothe gloss head,so that,for a given orientation,the position