1、Designation: C448 88 (Reapproved 2011)1Standard 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 rev
2、ision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1NOTETest Method was corrected editorially in 2011INTRODUCTIONThis test is a means of quantifying the abrasion resistance of porcelain ena
3、mels 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 porcelai
4、n 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 o
5、f 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 porcelainenam
6、els 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
7、 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 th
8、is 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 porcela
9、in 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 of abra-sive, and lot of calibrated plate glass standards used. Theadjusted slope is t
10、aken 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 continued abra-sion, the rate of wear increases unt
11、il it reaches a steady value.Thereafter, the rate of wear remains almost constant until theenamel is penetrated and the underlying ground coat or metalexposed. The abrasion that occurs during the period of increas-ing rate-of-weight loss is defined as surface abrasion andresults in reduced gloss and
12、 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
13、the coating. These two types ofabrasion are not necessarily proportional, and since it is1These 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
14、Systems.Current edition approved April 1, 2011. Published April 2011. Originallyapproved in 1959. Last previous edition approved in 2006 as C448 88 (2006).DOI: 10.1520/C0448-88R11E01.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.
15、org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.desirable to be able to determine the resistance of porcelainen
16、amel 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.5.2 Alloy Balls3Rust-resisting alloy balls of the type usedfor bearings,532 in. (4 mm) in diameter.About 4 lb (1.8 kg) arerequired
17、. 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 gi
18、ven orientation, the position ofthe specimen during the final gloss reading may be controlledto within116 in. (1.6 mm) of that during the original glossreading.NOTE 1Care should be taken to keep the interior of the glossmeterfree of dust. If a glossmeter is used with the opening at the top, a piece
19、ofphenolic resin or similar material should be placed over the opening whenthe instrument is not in use. The lenses should be cleaned at regularintervals with a soft camels-hair brush.The black gloss standard should be kept free of scratches, and should beprotected by wrapping with a soft cloth when
20、 not in use.5.4 Apparatus for Oscillating Specimens5The apparatusused for oscillating the specimens during test shall impart tonine specimens simultaneously a horizontal circular motionsuch that every point on each specimen describes a circle78 in.(22.2 mm) in diameter. The apparatus shall be provid
21、ed with anautomatic timing device capable of being preset to within 1 sof the desired time and shall operate at a frequency of 300 63 cpm (for machine manufactured prior to July 1981) or 345 63 cpm (for machines manufactured after July 1981). Theapparatus shall be operated on a firm and level surfac
22、e.5.5 Retaining RingsThe retaining rings shall be con-structed of metal lined with rubber. The inside height anddiameter of the rubber-lined ring shall be 1316 6116 in. (30.26 1.6 mm) and 3716 6116 in. (87.3 6 1.6 mm), respectively.Provision shall be made for clamping the retaining ring to anenamele
23、d metal specimen to produce a watertight seal. Meansshall be provided for introducing an abrasive charge after thespecimen is secured. Nine retaining rings are required.5.6 Buret, of suitable capacity to deliver 20 mL of water at20C (68F).6. Abrasives6.1 For the surface abrasion tests the 70 +100-me
24、sh frac-tion of Pennsylvania-type glass sand,6preferably as groundfrom quartzite (quartz rock), shall be used. For the subsurfaceabrasion test No. 80 grit aluminum oxide abrasive medium6shall be used.7. Reference Standards7.1 Specimens of standard calibrated polished plate glass6which shows a coeffi
25、cient of variation no greater than 1.5 %when tested for surface abrasion in accordance with theprocedure as specified in Section 10, and which meets require-ments of Table A1.4 shall be used as reference standards.8. Test Specimens8.1 Test specimens shall be 438 614 in. (111.1 6 6.4 mm)square, and m
26、ay be prepared by enameling metal blanks of thatsize or by cutting a larger piece. Specimens for the weight losstests should not exceed the capacity of the analytical balanceselected for obtaining the weights of the specimens. Whengloss measurements are to be made, the specimens testedshould be as f
27、lat and free of orange peel or wavy surface aspossible. Variations from flatness decrease the accuracy ofgloss measurements.8.2 Six specimens shall be tested for each determination ofresistance to surface abrasion or resistance to subsurfaceabrasion.9. Specimen Preparation9.1 Before making any measu
28、rements, wash each specimenwith a soft sponge moistened with a warm 1 % solution oftrisodium phosphate (distilled water not essential) and rinse inwarm, running tap water. If, when rinsing, the water gathers indrops on the surface, repeat the washing treatment until therinse water spreads evenly. Wh
29、ile the specimen is still wet,rinse it with ethyl alcohol. A small stream of alcohol from anordinary chemical wash bottle will suffice for rinsing. Pureethyl alcohol is preferable, but if it is not available, ethylalcohol that has been denatured with up to 5 % of a noncor-rosive, highly volatile org
30、anic compound such as methylalcohol may be used. Allow the specimens to air dry in avertical position and then place in a desiccator. This willprevent damage and moisture absorption of the specimenswhich can adversely affect the weight values. Gloss and weightdeterminations should be obtained within
31、 a 15-min period afterthe specimens have been cleaned and placed in the desiccator.NOTE 2Other denaturants, approved by the U. S. Bureau of InternalRevenue, that are not objectionable for this use are ethyl ether andbenzene, either alone or in combination with methyl alcohol. If ethylalcohol is not
32、available, isopropyl alcohol or acetone may be used, butpure ethyl alcohol is recommended if available. Avoid alcohol denaturedwith an ingredient of low volatility, which will remain as a surface film onthe specimen when used to rinse it before or after treatment. Surface filmsmay significantly affe
33、ct gloss readings.10. Resistance to Surface Abrasion of Porcelain EnamelsHaving 45 Specular Gloss of More than 30 GlossUnits10.1 Marking of Specimens and Determining Initial 45Specular GlossMark each specimen so that its orientationmay be controlled.Amark on the back at one edge will suffice.Place t
34、his edge against the specimen guide on the gloss head3Balls meeting the requirements of this paragraph are available from the MobayCorporation, 5601 Eastern Avenue, Baltimore, MD 21224.4Suitable instruments are available from: Pacific Scientific Company, Gardner/Neotec Instrument Division, 2431 Lind
35、en Lane, Silver Spring, MD 20910; andHunter Lab, 11495 Sunset Hills Road, Reston, VA 22090.5A suitable apparatus is the P.E.I. Abrasion Tester, manufactured by theKeystone Electric Co., 2807 Annapolis Road, Baltimore, MD 21230.6These standard materials are available from the Mobay Corp., 5601 Easter
36、nAve., Baltimore, MD 21224.C448 88 (2011)12for the first reading. Then make three other readings, turningthe specimen clockwise through 90 between readings.NOTE 3The measured gloss of light-transmitting specimens of suchmaterials as transparent or translucent glass or plastic may be affected bylight
37、 reflected from the back side of the specimen or transmitted throughthe specimen from the room. To minimize errors from this source, thefollowing precautions should be taken:(1) Roughen the back of transparent specimens to eliminate specularreflection from this surface.(2) Cover back and edges of li
38、ght-transmitting specimens with anopaque black cloth when measuring gloss to prevent normal roomillumination from being transmitted through the specimen, or light fromthe instrument from being reflected back through the specimen from alight surface in contact with the back of the specimen. This is p
39、articularlyimportant when using a glossmeter with the specimen holder on top.(3) Put no labels near the center of light-transmitting specimens.10.2 Determining Correct Abrasion Time The correctabrasion time is the time required to reduce the 45 speculargloss of a standard plate glass specimen to 53
40、6 1%.7Determine this time by abrading six standard plate glassspecimens and calculating the average percentage 45 speculargloss retained. A good trial time is 6.117 min (184 counts) onmachines manufactured prior to July 1981, or 4.367 min (150counts) on machines manufactured after July 1981.10.3 Sec
41、uring Specimens to Table of Abrasion Tester andIntroducing Abrasive MixtureCenter each specimen in oneof the nine available positions and secure by means of theretaining ring. Tighten the two wing nuts simultaneously anduniformly. The amount of tightening shall be just sufficient toprovide a waterti
42、ght seal between the retaining ring and thespecimen. Introduce an abrasive charge of 175 6 0.15 g of532-in. (4-mm) rust-resisting alloy balls, 3 6 0.01 g of 70 +100mesh Pennsylvania-type glass sand, and 20 6 0.2 mL of water,in that order, through the hole in the top of each retaining ring.After the
43、abrasive charge is introduced, seal the hole in the topof the retaining ring with a cork or rubber stopper.10.4 Treatment of SpecimensSet the automatic timingdevice for the previously determined time required to reducethe 45 specular gloss of a standard plate glass specimen to53 %. Set the selector
44、switch to the “automatic” position andclose the toggle switch, starting the oscillator. The abrasiontester will then stop after the prescribed abrasion time.10.5 Cleaning Specimens after Treatment:10.5.1 Clean the sample specimens and equipment as fol-lows:10.5.1.1 Immediately after treatment, loose
45、n the wing nutsthat secure the specimens to the abrasion tester. Carefullyremove the sample panel, retaining ring apparatus and abrasivemedium as a sealed unit. (This can be accomplished bycompressing the panel to the retaining ring apparatus with thehands and rotating the assembly from the confines
46、 of thesecuring posts of the abrasion tester. The ball bearings, theabrasive grit, and water can be discharged through a sieve thatwill allow the sand and water to pass through, but will retainthe ball bearings. This method facilitates the cleaning anddrying of the ball bearings so that they can be
47、used insubsequent testing cycles.) If any of the ball bearings aredropped and cannot be accounted for during the cleaning of theindividual retaining ring assemblies, another 175 6 0.15 g ofball bearings shall be used in subsequent testing cycles.10.5.1.2 Scrub the abraded portion very lightly with a
48、 cleansponge that has been saturated with warm water, rinse withwarm running water, and while still wet, rinse with alcohol andplace in a vertical position to dry.10.6 Determining Final 45 Specular GlossMake thefinal gloss readings within 15 min after the specimens havebeen given the final rinsing,
49、following the procedure outline in10.1.10.7 Computation of Surface Abrasion IndexFor each ofthe four orientations of the specimens, divide the final speculargloss reading by the initial reading and multiply by 100. Theaverage percentage residual specular gloss for the four posi-tions shall be taken as the surface abrasion index of thespecimen. The average index of six specimens after treatmentshall be taken as the abrasion index of a given index ofenameled metal.NOTE 4If it is desirable, nine samples may be treated simultaneously,this procedu
