ASTM C448-88(2021)

This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation: C448 − 88 (Reapproved 2021)
Standard Test Methods for
Abrasion Resistance of Porcelain Enamels
This standard is issued under the fixed designation C448; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
INTRODUCTION
Thistestisameansofquantifyingtheabrasionresistanceofporcelainenamelsthroughsteady-state
subsurfaceabrasivewearwithstainlesssteelballbearings.Achangeinglossorweightlossisreported
that can, through further evaluation, be correlated to the service life of the enameled ware.
1. Scope theoriginalspecularglossthatisretainedaftertreatmentasthe
surface abrasion index.
1.1 Thesetestmethodscoverdeterminationoftheresistance
of porcelain enamels to surface abrasion and subsurface
3.2 The second test is intended for the determination of the
abrasion.
resistance to surface abrasion of porcelain enamels for which
1.2 This standard does not purport to address all of the the unabraded 45° specular gloss is 30 gloss units or less. It
safety concerns, if any, associated with its use. It is the consists of determining the weight loss by a specified abrasive
responsibility of the user of this standard to establish appro-
treatment and multiplying this weight loss by an adjustment
priate safety, health, and environmental practices and deter-
factor associated with each abrasive tester, lot of abrasive, and
mine the applicability of regulatory limitations prior to use.
lot of calibrated plate glass standards used. The adjusted
1.3 This international standard was developed in accor-
weight loss is taken as an index of resistance to surface
dance with internationally recognized principles on standard-
abrasion.
ization established in the Decision on Principles for the
3.3 The third test is intended for the determination of the
Development of International Standards, Guides and Recom-
resistance of porcelain enamels to subsurface abrasion. It
mendations issued by the World Trade Organization Technical
consists of determining the slope of the linear portion of the
Barriers to Trade (TBT) Committee.
abrasion time-weight loss curve and multiplying by an adjust-
2. Referenced Documents
ment factor associated with each abrasion tester, lot of
abrasive, and lot of calibrated plate glass standards used. The
2.1 ASTM Standards:
adjusted slope is taken as an index of resistance to subsurface
C346Test Method for 45-deg Specular Gloss of Ceramic
abrasion.
Materials
3. Summary of Test Methods
4. Significance and Use
3.1 The first of the tests described herein is intended for the
4.1 Whenaporcelainenamelisfirstsubjectedtoabrasionof
determinationoftheresistancetosurfaceabrasionofporcelain
the type involved in these tests, the rate of wear or attrition is
enamels for which the unabraded 45° specular gloss is more
relatively low. As the enamel is subjected to continued
than 30 gloss units. It consists essentially of measuring the
abrasion, the rate of wear increases until it reaches a steady
specular gloss of the specimens before and after a specified
value. Thereafter, the rate of wear remains almost constant
abrasive treatment of the surface, and taking the percentage of
until the enamel is penetrated and the underlying ground coat
ormetalexposed.Theabrasionthatoccursduringtheperiodof
increasing rate-of-weight loss is defined as surface abrasion
These test methods are under the jurisdiction of ASTM Committee B08 on
Metallic and Inorganic Coatings and are the direct responsibility of Subcommittee
and results in reduced gloss and cleanability with high-gloss
B08.12 on Materials for Porcelain Enamel and Ceramic-Metal Systems.
enamels and a modification of color, appearance, or surface
Current edition approved April 1, 2021. Published May 2021. Originally
texture, or combination thereof with low-gloss enamels. The
approvedin1959.Lastpreviouseditionapprovedin2016asC448–88(2016).DOI:
10.1520/C0448-88R21.
abrasion that occurs during the period of steady rate-of-weight
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
loss is defined as subsurface abrasion and results in the
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
destruction of the continuity of the coating.These two types of
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. abrasion are not necessarily proportional, and since it is
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
C448 − 88 (2021)
desirable to be able to determine the resistance of porcelain from quartzite (quartz rock), shall be used. For the subsurface
enamel to both types of abrasion, it is necessary to deal with abrasion test No. 80 grit aluminum oxide abrasive medium
each one separately. shall be used.
5. Apparatus 7. Reference Standards
5.1 Balance, having a capacity of approximately 200 g and
7.1 Specimens of standard calibrated polished plate glass
accurate to 0.0001 g. which shows a coefficient of variation no greater than 1.5%
when tested for surface abrasion in accordance with the
5.2 Alloy Balls —Rust-resisting alloy balls of the type used
procedure as specified in Section 10, and which meets require-
forbearings, ⁄32in.(4mm)indiameter.About4lb(1.8kg)are
ments of Table A1.4 shall be used as reference standards.
required. Second-grade balls are satisfactory.
5.3 Apparatus for Measuring Specular Gloss, conforming
8. Test Specimens
to the requirements of Test Method C346 and having a
3 1
8.1 Test specimens shall be 4 ⁄8 6 ⁄4 in. (111.1 6 6.4 mm)
repeatable precision of not less than 60.5 gloss unit. Means
square,andmaybepreparedbyenamelingmetalblanksofthat
shall be provided for positioning the specimen, with respect to
size or by cutting a larger piece. Specimens for the weight loss
the gloss head, so that, for a given orientation, the position of
tests should not exceed the capacity of the analytical balance
the specimen during the final gloss reading may be controlled
selected for obtaining the weights of the specimens. When
to within ⁄16 in. (1.6 mm) of that during the original gloss
gloss measurements are to be made, the specimens tested
reading.
should be as flat and free of orange peel or wavy surface as
possible. Variations from flatness decrease the accuracy of
NOTE 1—Care should be taken to keep the interior of the glossmeter
free of dust. If a glossmeter is used with the opening at the top, a piece of
gloss measurements.
phenolicresinorsimilarmaterialshouldbeplacedovertheopeningwhen
8.2 Six specimens shall be tested for each determination of
the instrument is not in use. The lenses should be cleaned at regular
intervals with a soft camel’s-hair brush.
resistance to surface abrasion or resistance to subsurface
The black gloss standard should be kept free of scratches, and should
abrasion.
be protected by wrapping with a soft cloth when not in use.
9. Specimen Preparation
5.4 Apparatus for Oscillating Specimens —The apparatus
used for oscillating the specimens during test shall impart to
9.1 Before making any measurements, wash each specimen
nine specimens simultaneously a horizontal circular motion
with a soft sponge moistened with a warm 1% solution of
suchthateverypointoneachspecimendescribesacircle ⁄8in.
trisodium phosphate (distilled water not essential) and rinse in
(22.2mm)indiameter.Theapparatusshallbeprovidedwithan
warm, running tap water. If, when rinsing, the water gathers in
automatic timing device capable of being preset to within 1 s
drops on the surface, repeat the washing treatment until the
of the desired time and shall operate at a frequency of 300 6
rinse water spreads evenly. While the specimen is still wet,
3cpm(formachinemanufacturedpriortoJuly1981)or345 6
rinse it with ethyl alcohol. A small stream of alcohol from an
3 cpm (for machines manufactured after July 1981). The
ordinary chemical wash bottle will suffice for rinsing. Pure
apparatus shall be operated on a firm and level surface.
ethyl alcohol is preferable, but if it is not available, ethyl
alcohol that has been denatured with up to 5 % of a
5.5 Retaining Rings—The retaining rings shall be con-
noncorrosive, highly volatile organic compound such as
structed of metal lined with rubber. The inside height and
3 1
methyl alcohol may be used.Allow the specimens to air dry in
diameter of the rubber-lined ring shall be 1 ⁄16 6 ⁄16 in. (30.2
7 1
a vertical position and then place in a desiccator. This will
6 1.6 mm) and 3 ⁄16 6 ⁄16 in. (87.3 6 1.6 mm), respectively.
prevent damage and moisture absorption of the specimens
Provision shall be made for clamping the retaining ring to an
whichcanadverselyaffecttheweightvalues.Glossandweight
enameled metal specimen to produce a watertight seal. Means
determinationsshouldbeobtainedwithina15-minperiodafter
shall be provided for introducing an abrasive charge after the
the specimens have been cleaned and placed in the desiccator.
specimen is secured. Nine retaining rings are required.
5.6 Buret, of suitable capacity to deliver 20 mL of water at NOTE 2—Other denaturants, approved by the U. S. Bureau of Internal
Revenue, that are not objectionable for this use are ethyl ether and
20°C (68°F).
benzene, either alone or in combination with methyl alcohol. If ethyl
alcohol is not available, isopropyl alcohol or acetone may be used, but
6. Abrasives
pure ethyl alcohol is recommended if available. Avoid alcohol denatured
6.1 For the surface abrasion tests the−70 +100-mesh frac- withaningredientoflowvolatility,whichwillremainasasurfacefilmon
thespecimenwhenusedtorinseitbeforeoraftertreatment.Surfacefilms
tion of Pennsylvania-type glass sand, preferably as ground
may significantly affect gloss readings.
10. Resistance to Surface Abrasion of Porcelain Enamels
Balls meeting the requirements of this paragraph are available from the Mobay
Corporation, 5601 Eastern Avenue, Baltimore, MD 21224.
Having 45° Specular Gloss of More than 30 Gloss
Suitable instruments are available from: Pacific Scientific Company, Gardner/
Units
Neotec Instrument Division, 2431 Linden Lane, Silver Spring, MD 20910; and
Hunter Lab, 11495 Sunset Hills Road, Reston, VA 22090.
10.1 Marking of Specimens and Determining Initial 45°
A suitable apparatus is the P.E.I. Abrasion Tester, manufactured by the
Specular Gloss—Mark each specimen so that its orientation
Keystone Electric Co., 2807 Annapolis Road, Baltimore, MD 21230.
maybecontrolled.Amarkonthebackatoneedgewillsuffice.
These standard materials are available from the Mobay Corp., 5601 Eastern
Ave., Baltimore, MD 21224. Place this edge against the specimen guide on the gloss head
C448 − 88 (2021)
for the first reading. Then make three other readings, turning drying of the ball bearings so that they can be used in
the specimen clockwise through 90° between readings. subsequent testing cycles.) If any of the ball bearings are
droppedandcannotbeaccountedforduringthecleaningofthe
NOTE 3—The measured gloss of light-transmitting specimens of such
individual retaining ring assemblies, another 175 6 0.15 g of
materials as transparent or translucent glass or plastic may be affected by
ball bearings shall be used in subsequent testing cycles.
light reflected from the back side of the specimen or transmitted through
the specimen from the room. To minimize errors from this source, the
10.5.1.2 Scrub the abraded portion very lightly with a clean
following precautions should be taken:
sponge that has been saturated with warm water, rinse with
(1)Roughen the back of transparent specimens to eliminate specular
warmrunningwater,andwhilestillwet,rinsewithalcoholand
reflection from this surface.
place in a vertical position to dry.
(2)Cover back and edges of light-transmitting specimens with an
opaque black cloth when measuring gloss to prevent normal room
10.6 DeterminingFinal45°SpecularGloss—Makethefinal
illumination from being transmitted through the specimen, or light from
gloss readings within 15 min after the specimens have been
the instrument from being reflected back through the specimen from a
light surface in contact with the back of the specimen.This is particularly giventhefinalrinsing,followingtheprocedureoutlinein10.1.
important when using a glossmeter with the specimen holder on top.
10.7 Computation of Surface Abrasion Index—For each of
(3)Put no labels near the center of light-transmitting specimens.
thefourorientationsofthespecimens,dividethefinalspecular
10.2 Determining Correct Abrasion Time— The correct
gloss reading by the initial reading and multiply by 100. The
abrasion time is the time required to reduce the 45° specular
7 average percentage residual specular gloss for the four posi-
gloss of a standard plate glass specimen to 53 6 1%.
tions shall be taken as the surface abrasion index of the
Determine this time by abrading six standard plate glass
specimen. The average index of six specimens after treatment
specimens and calculating the average percentage 45° specular
shall be taken as the abrasion index of a given index of
gloss retained. A good trial time is 6.117 min (184 counts) on
enameled metal.
machines manufactured prior to July 1981, or 4.367 min (150
counts) on machines manufactured after July 1981.
NOTE 4—If it is desirable, nine samples may be treated simultaneously,
this procedure being repeated until six specimens of each sample have
10.3 Securing Specimens to Table of Abrasion Tester and
been tested. If less than nine samples are to be tested, any arrangement
IntroducingAbrasiveMixture—Centereachspecimeninoneof
desired may be used and the arrangement may be such that the number of
the nine available positions and secure by means of the
operations required to test six specimens of each sample is a minimum.
retaining ring. Tighten the two wing nuts simultaneously and
10.8 Use of Standard Plate Glass Specimens—As a check
uniformly. The amount of tightening shall be just sufficient to
on the performance of the apparatus, test standard, calibrated,
provide a watertight seal between the retaining ring and the
plate glass specimens at regular intervals. If the computed
specimen. Introduce an abrasive charge of 175 6 0.15 g of ⁄32
surface abrasion index obtained in a check test of six standard
-in. (4-mm) rust-resisting alloy balls, 3 6 0.01 g of−70+100
glass plates falls outside the limits 52.0 to 54.0 but within the
meshPennsylvania-typeglasssand,and20 60.2mLofwater,
limits51.5to54.5,adjusttheabrasiontimeinaccordancewith
in that order, through the hole in the top of each retaining ring.
10.2.Ifavaluebelow51.5orabove54.5isobtained,defective
After the abrasive charge is introduced, seal the hole in the top
technique or equipment is indicated, and the source of diffi-
of the retaining ring with a cork or rubber stopper.
culty should be found and remedied.
10.4 Treatment of Specimens—Set the automatic timing
NOTE 5—This check test need not be made each time enameled metal
device for the previously determined time required to reduce
specimens are tested.The time between check tests will be determined by
the 45° specular gloss of a standard plate glass specimen to
the number of tests made by the laboratory.
53%. Set the selector switch to the “automatic” position and
close the toggle switch, starting the oscillator. The abrasion
11. Resistance to Surface Abrasion of Porcelain Enamels
tester will then stop after the prescribed abrasion time.
Having 45° Specular Gloss of 30 Gloss Units or Less
10.5 Cleaning Specimens after Treatment:
11.1 Determining Initial Weight of Specimens—Weigh each
10.5.1 Clean the sample specimens and equipment as fol-
specimen to the nearest 0.1 mg within 15 min after it has been
lows:
rinsed with alcohol.
10.5.1.1 Immediately after treatment, loosen the wing nuts
that secure the specimens to the abrasion tester. Carefully NOTE 6—When weight determinations are to be made, the specimens
should be handled with care to prevent chipping, which may introduce
removethesamplepanel,retainingringapparatusandabrasive
significanterrors.Thisprecautionisparticularlyimportantforglassplates,
medium as a sealed unit. (This can be accomplished by
and in determining surface abrasion by weight loss.
compressing the panel to the retaining ring apparatus with the
11.2 Securing Specimens to Table of Abrasion Tester and
hands and rotating the assembly from the confines of the
Introducing Abrasive Mixture—Secure the test specimens to
securing posts of the abrasion tester. The ball bearings, the
the table of the abrasion tester and introduce the abrasive
abrasive grit, and water can be discharged through a sieve that
mixture in accordance with 10.3.
will allow the sand and water to pass through, but will retain
the ball bearings. This method facilitates the cleaning and
11.3 Treatment of Specimens—Set the selector switch to the
“automatic” position, set the automatic timing device for 10
min (300 counts) on machines manufactured prior to July
This value may change slightly from time to time when it is necessary to
1981, or 10 min (342 counts) on machines manufactured after
replenish the supply of standards. In any case, the corrected value will be furnished
with each lot of standards (see Annex A4). July 1981.
C448 − 88 (2021)
11.4 CleaningSpecimensAfterTreatment—Aftertreatment, Allow the specimens to air dry in a vertical position and then
clean the specimens in accordance with 10.5. If the retaining place them in a desiccator.
ring has left a black mark on the specimen, this may be 12.7.2 For each specimen, subtract the weight at the end of
removed by scrubbing lightly with a soft sponge. Do not scrub eight 15-min periods, W , from the weight at the end of four
the abraded area. 15-min periods, W , and divide by 60 to obtain the rate-of-
weight loss.
11.5 Determining Final Weight of Specimens—Determine
12.7.3 Calculate the average rate-of-weight loss for the 24
the final weight of each specimen in accordance with 11.1.
specimens.
11.6 Computation of Surface Abrasion Index—For each
12.7.4 Divide this average rate-of-weight loss for the last
specimen, multiply the weight loss by an adjustment factor
four 15-min periods into 4.5671 (see AnnexA4).An example
determined as specified in 12.7, but using Pennsylvania-type
is given in Table 1.
glass sand. The average adjusted weight loss is taken as the
12.8 Calculation of Subsurface Abrasion Index—For each
surface abrasion index of the enamel (Note 4).
specimen, subtract the weight after 45 min of abrasion, W ,
11.7 Use of Standard Plate Glass Specimens—As a check
from the weight after 15 min of abrasion, W , and divide the
on the performance of the apparatus, test standard, calibrated
difference by 30. The quotient, X, is the slope of the linear
t
plate glass specimens at regular intervals in accordance with
portion of the abrasion time - weight loss curve and shall be
10.8 (Note 5).
taken as the true rate-of-weight loss of the specimen as
determined by the laboratory with its particular abrasion tester.
12. Resistance to Subsurface Abrasion
The true rate-of-weight loss for each specimen shall then be
multiplied by the adjustment factor determined in accordance
12.1 Determining Initial Weight of Specimens—Determine
¯
with 12.7, giving an adjusted rate-of-weight loss, X . The
the initial weight of each specimen in accordance with 11.1. a
average adjusted rate-of-weight loss shall be taken as the
12.2 Securing Specimens to Table of Abrasion Tester and
subsurface abrasion index of the ena
...