ASTM C448-88(1999)
(Test Method)Standard Test Methods for Abrasion Resistance of Porcelain Enamels
Standard Test Methods for Abrasion Resistance of Porcelain Enamels
SCOPE
1.1 These test methods cover determination of the resistance of porcelain enamels to surface abrasion and subsurface abrasion.
1.2 This standard may involve hazardous materials, operations, and equipment. This standard does not purport to address all of the safety problems associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
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Designation: C 448 – 88 (Reapproved 1999)
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 (e) indicates an editorial change since the last revision or reapproval.
1. Scope sive, and lot of calibrated plate glass standards used. The
adjusted slope is taken as an index of resistance to subsurface
1.1 Thesetestmethodscoverdeterminationoftheresistance
abrasion.
of porcelain enamels to surface abrasion and subsurface
abrasion.
4. Significance and Use
1.2 This standard does not purport to address all of the
4.1 Whenaporcelainenamelisfirstsubjectedtoabrasionof
safety concerns, if any, associated with its use. It is the
the type involved in these tests, the rate of wear or attrition is
responsibility of the user of this standard to establish appro-
relatively low. As the enamel is subjected to continued abra-
priate safety and health practices and determine the applica-
sion, the rate of wear increases until it reaches a steady value.
bility of regulatory limitations prior to use.
Thereafter, the rate of wear remains almost constant until the
2. Referenced Documents enamel is penetrated and the underlying ground coat or metal
exposed.Theabrasionthatoccursduringtheperiodofincreas-
2.1 ASTM Standards:
ing rate-of-weight loss is defined as surface abrasion and
C346 Test Method for 45-deg Specular Gloss of Ceramic
results in reduced gloss and cleanability with high-gloss
Materials
enamels and a modification of color, appearance, or surface
3. Summary of Test Methods
texture, or combination thereof with low-gloss enamels. The
abrasion that occurs during the period of steady rate-of-weight
3.1 The first of the tests described herein is intended for the
loss is defined as subsurface abrasion and results in the
determinationoftheresistancetosurfaceabrasionofporcelain
destruction of the continuity of the coating.These two types of
enamels for which the unabraded 45° specular gloss is more
abrasion are not necessarily proportional, and since it is
than 30 gloss units. It consists essentially of measuring the
desirable to be able to determine the resistance of porcelain
specular gloss of the specimens before and after a specified
enamel to both types of abrasion, it is necessary to deal with
abrasive treatment of the surface, and taking the percentage of
each one separately.
theoriginalspecularglossthatisretainedaftertreatmentasthe
surface abrasion index.
5. Apparatus
3.2 The second test is intended for the determination of the
5.1 Balance, having a capacity of approximately 200 g and
resistance to surface abrasion of porcelain enamels for which
accurate to 0.0001 g.
the unabraded 45° specular gloss is 30 gloss units or less. It
5.2 Alloy Balls —Rust-resisting alloy balls of the type used
consists of determining the weight loss by a specified abrasive
forbearings, ⁄32in.(4mm)indiameter.About4lb(1.8kg)are
treatment and multiplying this weight loss by an adjustment
required. Second-grade balls are satisfactory.
factor associated with each abrasive tester, lot of abrasive, and
5.3 Apparatus for Measuring Specular Gloss, conforming
lot of calibrated plate glass standards used. The adjusted
to the requirements of Test Method C346 and having a
weight loss is taken as an index of resistance to surface
repeatable precision of not less than 6 0.5 gloss unit. Means
abrasion.
shall be provided for positioning the specimen, with respect to
3.3 The third test is intended for the determination of the
the gloss head, so that, for a given orientation, the position of
resistance of porcelain enamels to subsurface abrasion. It
the specimen during the final gloss reading may be controlled
consists of determining the slope of the linear portion of the
to within ⁄16 in. (1.6 mm) of that during the original gloss
abrasion time-weight loss curve and multiplying by an adjust-
reading.
ment factor associated with each abrasion tester, lot of abra-
NOTE 1—Care should be taken to keep the interior of the glossmeter
These test methods are under the jurisdiction of ASTM Committee B-8 on
Metallic and Inorganic Coatings and are the direct responsibility of Subcommittee Balls meeting the requirements of this paragraph are available from the Mobay
B08.12 on Materials for Porcelain Enamel and Ceramic-Metal Systems. Corporation, 5601 Eastern Avenue, Baltimore, MD 21224.
Current edition approved Feb. 26, 1988. Published May 1988. Originally Suitable instruments are available from: Pacific Scientific Company, Gardner/
published as C448–59T. Last previous edition C448–81. Neotec Instrument Division, 2431 Linden Lane, Silver Spring, MD 20910; and
Annual Book of ASTM Standards, Vol 02.05. Hunter Lab, 11495 Sunset Hills Road, Reston, VA 22090.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
C 448 – 88 (1999)
free of dust. If a glossmeter is used with the opening at the top, a piece of
9. Specimen Preparation
phenolicresinorsimilarmaterialshouldbeplacedovertheopeningwhen
9.1 Before making any measurements, wash each specimen
the instrument is not in use. The lenses should be cleaned at regular
with a soft sponge moistened with a warm 1% solution of
intervals with a soft camel’s-hair brush.
trisodium phosphate (distilled water not essential) and rinse in
Theblackglossstandardshouldbekeptfreeofscratches,andshouldbe
protected by wrapping with a soft cloth when not in use. warm, running tap water. If, when rinsing, the water gathers in
drops on the surface, repeat the washing treatment until the
5.4 Apparatus for Oscillating Specimens —The apparatus
rinse water spreads evenly. While the specimen is still wet,
used for oscillating the specimens during test shall impart to
rinse it with ethyl alcohol. A small stream of alcohol from an
nine specimens simultaneously a horizontal circular motion
ordinary chemical wash bottle will suffice for rinsing. Pure
suchthateverypointoneachspecimendescribesacircle ⁄8in.
ethyl alcohol is preferable, but if it is not available, ethyl
(22.2mm)indiameter.Theapparatusshallbeprovidedwithan
alcohol that has been denatured with up to 5% of a noncor-
automatic timing device capable of being preset to within 1 s
rosive, highly volatile organic compound such as methyl
of the desired time and shall operate at a frequency of 3006 3
alcohol may be used. Allow the specimens to air dry in a
cpm (for machine manufactured prior to July 1981) or 345 6
vertical position and then place in a desiccator. This will
3 cpm (for machines manufactured after July 1981). The
prevent damage and moisture absorption of the specimens
apparatus shall be operated on a firm and level surface.
whichcanadverselyaffecttheweightvalues.Glossandweight
5.5 Retaining Rings—The retaining rings shall be con-
determinationsshouldbeobtainedwithina15-minperiodafter
structed of metal lined with rubber. The inside height and
the specimens have been cleaned and placed in the desiccator.
3 1
diameter of the rubber-lined ring shall be 1 ⁄16 6 ⁄16 in. (30.2
7 1
6 1.6 mm) and 3 ⁄16 6 ⁄16 in. (87.3 6 1.6 mm), respectively.
NOTE 2—Other denaturants, approved by the U. S. Bureau of Internal
Provision shall be made for clamping the retaining ring to an Revenue, that are not objectionable for this use are ethyl ether and
benzene, either alone or in combination with methyl alcohol. If ethyl
enameled metal specimen to produce a watertight seal. Means
alcohol is not available, isopropyl alcohol or acetone may be used, but
shall be provided for introducing an abrasive charge after the
pure ethyl alcohol is recommended if available. Avoid alcohol denatured
specimen is secured. Nine retaining rings are required.
withaningredientoflowvolatility,whichwillremainasasurfacefilmon
5.6 Buret, of suitable capacity to deliver 20 mL of water at
thespecimenwhenusedtorinseitbeforeoraftertreatment.Surfacefilms
20°C (68°F).
may significantly affect gloss readings.
6. Abrasives
10. Resistance to Surface Abrasion of Porcelain Enamels
Having 45° Specular Gloss of More than 30 Gloss
6.1 For the surface abrasion tests the−70 +100-mesh frac-
Units
tion of Pennsylvania-type glass sand, preferably as ground
from quartzite (quartz rock), shall be used. For the subsurface
10.1 Marking of Specimens and Determining Initial 45°
abrasion test No. 80 grit aluminum oxide abrasive medium
Specular Gloss—Mark each specimen so that its orientation
shall be used.
maybecontrolled.Amarkonthebackatoneedgewillsuffice.
Place this edge against the specimen guide on the gloss head
7. Reference Standards
for the first reading. Then make three other readings, turning
7.1 Specimens of standard calibrated polished plate glass
the specimen clockwise through 90° between readings.
which shows a coefficient of variation no greater than 1.5%
NOTE 3—The measured gloss of light-transmitting specimens of such
when tested for surface abrasion in accordance with the
materials as transparent or translucent glass or plastic may be affected by
procedure as specified in Section 10, and which meets require-
light reflected from the back side of the specimen or transmitted through
ments of Table A1.4 shall be used as reference standards.
the specimen from the room. To minimize errors from this source, the
following precautions should be taken:
8. Test Specimens
(1) Roughen the back of transparent specimens to eliminate specular
3 1 reflection from this surface.
8.1 Test specimens shall be 4 ⁄8 6 ⁄4 in. (111.1 6 6.4 mm)
(2) Cover back and edges of light-transmitting specimens with an
square,andmaybepreparedbyenamelingmetalblanksofthat
opaque black cloth when measuring gloss to prevent normal room
size or by cutting a larger piece. Specimens for the weight loss
illumination from being transmitted through the specimen, or light from
tests should not exceed the capacity of the analytical balance
the instrument from being reflected back through the specimen from a
selected for obtaining the weights of the specimens. When
light surface in contact with the back of the specimen.This is particularly
gloss measurements are to be made, the specimens tested important when using a glossmeter with the specimen holder on top.
(3) Put no labels near the center of light-transmitting specimens.
should be as flat and free of orange peel or wavy surface as
possible. Variations from flatness decrease the accuracy of
10.2 Determining Correct Abrasion Time— The correct
gloss measurements.
abrasion time is the time required to reduce the 45° specular
8.2 Six specimens shall be tested for each determination of
gloss of a standard plate glass specimen to 53 6 1%.
resistance to surface abrasion or resistance to subsurface
Determine this time by abrading six standard plate glass
abrasion.
specimens and calculating the average percentage 45° specular
A suitable apparatus is the P.E.I. Abrasion Tester, manufactured by the
Keystone Electric Co., 2807 Annapolis Road, Baltimore, MD 21230. This value may change slightly from time to time when it is necessary to
These standard materials are available from the Mobay Corp., 5601 Eastern replenish the supply of standards. In any case, the corrected value will be furnished
Ave., Baltimore, MD 21224. with each lot of standards (see Annex A4).
C 448 – 88 (1999)
desired may be used and the arrangement may be such that the number of
gloss retained. A good trial time is 6.117 min (184 counts) on
operations required to test six specimens of each sample is a minimum.
machines manufactured prior to July 1981, or 4.367 min (150
counts) on machines manufactured after July 1981.
10.8 Use of Standard Plate Glass Specimens—As a check
10.3 Securing Specimens to Table of Abrasion Tester and
on the performance of the apparatus, test standard, calibrated,
Introducing Abrasive Mixture—Center each specimen in one
plate glass specimens at regular intervals. If the computed
of the nine available positions and secure by means of the
surface abrasion index obtained in a check test of six standard
retaining ring. Tighten the two wing nuts simultaneously and
glass plates falls outside the limits 52.0 to 54.0 but within the
uniformly. The amount of tightening shall be just sufficient to
limits 51.5 to 54.5, adjust the abrasion time in accordance with
provide a watertight seal between the retaining ring and the
10.2.Ifavaluebelow51.5orabove54.5isobtained,defective
specimen. Introduce an abrasive charge of 175 6 0.15 g of ⁄32
technique or equipment is indicated, and the source of diffi-
-in. (4-mm) rust-resisting alloy balls, 3 6 0.01 g of−70+100
culty should be found and remedied.
meshPennsylvania-typeglasssand,and20 60.2mLofwater,
NOTE 5—This check test need not be made each time enameled metal
in that order, through the hole in the top of each retaining ring.
specimens are tested.The time between check tests will be determined by
After the abrasive charge is introduced, seal the hole in the top
the number of tests made by the laboratory.
of the retaining ring with a cork or rubber stopper.
10.4 Treatment of Specimens—Set the automatic timing
11. Resistance to Surface Abrasion of Porcelain Enamels
device for the previously determined time required to reduce
Having 45° Specular Gloss of 30 Gloss Units or Less
the 45° specular gloss of a standard plate glass specimen to
11.1 Determining Initial Weight of Specimens—Weigh each
53%. Set the selector switch to the “automatic” position and
specimen to the nearest 0.1 mg within 15 min after it has been
close the toggle switch, starting the oscillator. The abrasion
rinsed with alcohol.
tester will then stop after the prescribed abrasion time.
10.5 Cleaning Specimens after Treatment:
NOTE 6—When weight determinations are to be made, the specimens
10.5.1 Clean the sample specimens and equipment as fol- should be handled with care to prevent chipping, which may introduce
significanterrors.Thisprecautionisparticularlyimportantforglassplates,
lows:
and in determining surface abrasion by weight loss.
10.5.1.1 Immediately after treatment, loosen the wing nuts
that secure the specimens to the abrasion tester. Carefully
11.2 Securing Specimens to Table of Abrasion Tester and
removethesamplepanel,retainingringapparatusandabrasive
Introducing Abrasive Mixture—Secure the test specimens to
medium as a sealed unit. (This can be accomplished by
the table of the abrasion tester and introduce the abrasive
compressing the panel to the retaining ring apparatus with the
mixture in accordance with 10.3
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