1、Designation: C 448 88 (Reapproved 2006)Standard Test Methods forAbrasion Resistance of Porcelain Enamels1This standard is issued under the fixed designation C 448; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last re
2、vision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 These test methods cover determination of the resistanceof porcelain enamels to surface abrasion and subsurfaceabrasion.1.2
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 Docum
4、ents2.1 ASTM Standards:2C 346 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 moretha
5、n 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 intend
6、ed 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 ea
7、ch 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 determi
8、ning 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 taken as an index of resistance to subsurfaceabrasion.4.
9、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 until it reaches a steady value.Thereafter, the rate of wea
10、r 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 cleanability with high-glossenamels and a modification
11、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 necessar
12、ily 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.5.2 Alloy Balls3Rust-resisting all
13、oy balls of the type usedfor bearings,532 in. (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 C 346 and having arepeatable precision of not less than 60.5 gloss unit. Mean
14、sshall be provided for positioning the specimen, with respect tothe gloss head, so that, for a given orientation, the position of1These test methods are under the jurisdiction of ASTM Committee B08 onMetallic and Inorganic Coatings and are the direct responsibility of SubcommitteeB08.12 on Materials
15、 for Porcelain Enamel and Ceramic-Metal Systems.Current edition approved April 1, 2006. Published May 2006. Originallyapproved in 1959. Last previous edition approved in 1999 as C 448 88 (1999).2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at s
16、erviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.3Balls meeting the requirements of this paragraph are available from the MobayCorporation, 5601 Eastern Avenue, Baltimore, MD 21224.4Suitable instruments are available
17、 from: Pacific Scientific Company, Gardner/Neotec Instrument Division, 2431 Linden Lane, Silver Spring, MD 20910; andHunter Lab, 11495 Sunset Hills Road, Reston, VA 22090.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.the specimen d
18、uring 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 ofphenolic resin or similar material should be
19、 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 not in use.5.4 Apparatus for Oscillating Spec
20、imens5The 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 provided with anautomatic timing device capable of b
21、eing 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 surface.5.5 Retaining RingsThe retaining rings shall
22、 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 anenameled metal specimen to produce a watertight seal.
23、 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-mesh frac-tion of Pennsylvania-type glass sand,6
24、preferably 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 coefficient of variation no greater than 1.5 %when t
25、ested 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 may be prepared by enameling metal blanks of th
26、atsize 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 flat and free of orange peel or wavy surface as
27、possible. 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 measurements, wash each specimenwith a soft sponge
28、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. While the specimen is still wet,rinse it with et
29、hyl 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 organic compound such as methylalcohol may be use
30、d. 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 a 15-min period afterthe specimens have been
31、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 available, isopropyl alcohol or acetone may be
32、 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 affect gloss readings.10. Resistance to Surface Ab
33、rasion 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 this edge against the specimen guide on the glo
34、ss headfor 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 reflected from the back side of the
35、 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 light-transmitting specimens with anop
36、aque 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 particularlyimportant when using a gl
37、ossmeter 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 specular5A suitable apparatus is the P.E.I. Abrasion Tester, manufactured by theKeystone El
38、ectric Co., 2807 Annapolis Road, Baltimore, MD 21230.6These standard materials are available from the Mobay Corp., 5601 EasternAve., Baltimore, MD 21224.C 448 88 (2006)2gloss of a standard plate glass specimen to 53 6 1%.7Determine this time by abrading six standard plate glassspecimens and calculat
39、ing 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 Securing Specimens to Table of Abrasion Tester andIntroducing Abrasive MixtureCenter ea
40、ch 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 watertight seal between the retaining ring and thespecimen. Introduce an abrasive charge of
41、 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 abrasive charge is introduced, seal the hole in the topof the retaining ring with a
42、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 switch to the “automatic” position andclose the toggle switch, starting the oscillat
43、or. 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, loosen the wing nutsthat secure the specimens to the abrasion tester. Carefullyremove the
44、 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 of thesecuring posts of the abrasion tester. The ball bearings, theabrasive grit, a
45、nd 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 used insubsequent testing cycles.) If any of the ball bearings aredropped and cannot
46、 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 cleansponge that has been saturated with warm water, rinse withwarm running water,
47、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, following the procedure outline in10.1.10.7 Computation of Surface Abrasion IndexFor
48、 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 aft
49、er 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 procedure being repeated until six specimens of each sample havebeen tested. If less than nine samples are to be tested, any arrangementdesired may be used and the arrangement may be such that the number ofoperations required to test six specimens of each sample is a minimum.10.8 Use of Standard Plate Glass SpecimensAs a checkon the performance of the apparatus, test standard, calibrated,plat
