1、Designation: C448 88 (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 revi
2、sion. 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 w
3、ith 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 subsurfaceabrasio
4、n.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
5、 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 mo
6、rethan 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 i
7、ntended 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 wi
8、th 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 de
9、termining 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.
10、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 we
11、ar 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 o
12、f 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 necessari
13、ly 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 j
14、urisdiction 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 ap
15、proved 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.Cop
16、yright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States15.2 Alloy Balls3Rust-resisting alloy 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 Mea
17、suring 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 ofthe specimen during the fin
18、al 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 placed over
19、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 shouldbe protected by wrapping with a soft cloth when not in use.5.4 Apparatus for Oscillating Specimens5The app
20、aratusused 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 being preset t
21、o 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 be con-struc
22、ted 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. Meansshall b
23、e 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,6preferably as
24、 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 tested for sur
25、face 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 thatsize or by
26、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 aspossible. Var
27、iations 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 moistened wit
28、h 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 ethyl alcohol.
29、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 anoncorrosive, highly volatile organic compound such asmethyl alcohol may be used. Allow the sp
30、ecimens to air dry ina vertical 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 cleaned and pla
31、ced 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 used, butpure
32、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 Abrasion of Porce
33、lain 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 gloss headfor the
34、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 specimen or tr
35、ansmitted throughthe specimen from the room. To minimize errors from this source, thefollowing precautions should be taken:3Balls meeting the requirements of this paragraph are available from the MobayCorporation, 5601 Eastern Avenue, Baltimore, MD 21224.4Suitable instruments are available from: Pac
36、ific Scientific Company, Gardner/Neotec Instrument Division, 2431 Linden 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 21230.6Th
37、ese standard materials are available from the Mobay Corp., 5601 EasternAve., Baltimore, MD 21224.C448 88 (2016)2(1) Roughen the back of transparent specimens to eliminatespecular reflection from this surface.(2) Cover back and edges of light-transmitting specimenswith an opaque black cloth when meas
38、uring gloss to preventnormal room illumination from being transmitted through thespecimen, or light from the instrument from being reflectedback through the specimen from a light surface in contact withthe back of the specimen. This is particularly important whenusing a glossmeter with the specimen
39、holder on top.(3) Put no labels near the center of light-transmittingspecimens.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 6 1%.7Determine this time by abrading six standard plate glasssp
40、ecimens 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 Securing Specimens to Table of Abrasion Tester andIntroducing Abras
41、ive MixtureCenter each specimen in one ofthe 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 a
42、n 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 abrasive charge is introduced, seal the hole in the topof the re
43、taining 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 switch to the “automatic” position andclose the toggle switch, s
44、tarting 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, loosen the wing nutsthat secure the specimens to the abrasion tester.
45、 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 of thesecuring posts of the abrasion tester. The ball bearings,
46、 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 used insubsequent testing cycles.) If any of the ball bearings a
47、redropped 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 cleansponge that has been saturated with warm water, rinse with
48、warm running water, and while still wet, rinse with alcohol andplace in a vertical position to dry.10.6 Determining Final 45 Specular GlossMake the finalgloss readings within 15 min after the specimens have beengiven the final rinsing, following the procedure outline in 10.1.10.7 Computation of Surf
49、ace 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 procedure being repeated until six specimens of each sample havebeen teste
