ASTM C448-88(2006)
(Test Method)Standard Test Methods for Abrasion Resistance of Porcelain Enamels
Standard Test Methods for Abrasion Resistance of Porcelain Enamels
SIGNIFICANCE AND USE
When a porcelain enamel is first subjected to abrasion of the type involved in these tests, the rate of wear or attrition is relatively low. As the enamel is subjected to continued abrasion, the rate of wear increases until it reaches a steady value. Thereafter, the rate of wear remains almost constant until the enamel is penetrated and the underlying ground coat or metal exposed. The abrasion that occurs during the period of increasing rate-of-weight loss is defined as surface abrasion and results in reduced gloss and cleanability with high-gloss enamels and a modification of color, appearance, or surface texture, or combination thereof with low-gloss enamels. The abrasion that occurs during the period of steady rate-of-weight loss is defined as subsurface abrasion and results in the destruction of the continuity of the coating. These two types of abrasion are not necessarily proportional, and since it is desirable to be able to determine the resistance of porcelain enamel to both types of abrasion, it is necessary to deal with each one separately.
SCOPE
1.1 These test methods cover determination of the resistance of porcelain enamels to surface abrasion and subsurface abrasion.
This standard does not purport to address all of the safety concerns, if any, 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: C448 – 88 (Reapproved 2006)
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.
1. Scope 3.3 The third test is intended for the determination of the
resistance of porcelain enamels to subsurface abrasion. It
1.1 Thesetestmethodscoverdeterminationoftheresistance
consists of determining the slope of the linear portion of the
of porcelain enamels to surface abrasion and subsurface
abrasion time-weight loss curve and multiplying by an adjust-
abrasion.
ment factor associated with each abrasion tester, lot of abra-
1.2 This standard does not purport to address all of the
sive, and lot of calibrated plate glass standards used. The
safety concerns, if any, associated with its use. It is the
adjusted slope is taken as an index of resistance to subsurface
responsibility of the user of this standard to establish appro-
abrasion.
priate safety and health practices and determine the applica-
bility of regulatory limitations prior to use.
4. Significance and Use
2. Referenced Documents 4.1 Whenaporcelainenamelisfirstsubjectedtoabrasionof
the type involved in these tests, the rate of wear or attrition is
2.1 ASTM Standards:
relatively low. As the enamel is subjected to continued abra-
C346 Test Method for 45-deg Specular Gloss of Ceramic
sion, the rate of wear increases until it reaches a steady value.
Materials
Thereafter, the rate of wear remains almost constant until the
3. Summary of Test Methods
enamel is penetrated and the underlying ground coat or metal
exposed.Theabrasionthatoccursduringtheperiodofincreas-
3.1 The first of the tests described herein is intended for the
ing rate-of-weight loss is defined as surface abrasion and
determinationoftheresistancetosurfaceabrasionofporcelain
results in reduced gloss and cleanability with high-gloss
enamels for which the unabraded 45° specular gloss is more
enamels and a modification of color, appearance, or surface
than 30 gloss units. It consists essentially of measuring the
texture, or combination thereof with low-gloss enamels. The
specular gloss of the specimens before and after a specified
abrasion that occurs during the period of steady rate-of-weight
abrasive treatment of the surface, and taking the percentage of
loss is defined as subsurface abrasion and results in the
theoriginalspecularglossthatisretainedaftertreatmentasthe
destructionofthecontinuityofthecoating.Thesetwotypesof
surface abrasion index.
abrasion are not necessarily proportional, and since it is
3.2 The second test is intended for the determination of the
desirable to be able to determine the resistance of porcelain
resistance to surface abrasion of porcelain enamels for which
enamel to both types of abrasion, it is necessary to deal with
the unabraded 45° specular gloss is 30 gloss units or less. It
each one separately.
consists of determining the weight loss by a specified abrasive
treatment and multiplying this weight loss by an adjustment
5. Apparatus
factor associated with each abrasive tester, lot of abrasive, and
5.1 Balance, having a capacity of approximately 200 g and
lot of calibrated plate glass standards used. The adjusted
accurate to 0.0001 g.
weight loss is taken as an index of resistance to surface
5.2 Alloy Balls —Rust-resisting alloy balls of the type used
abrasion.
forbearings, ⁄32in.(4mm)indiameter.About4lb(1.8kg)are
required. Second-grade balls are satisfactory.
5.3 Apparatus for Measuring Specular Gloss, conforming
These test methods are under the jurisdiction of ASTM Committee B08 on
to the requirements of Test Method C346 and having a
Metallic and Inorganic Coatings and are the direct responsibility of Subcommittee
repeatable precision of not less than 60.5 gloss unit. Means
B08.12 on Materials for Porcelain Enamel and Ceramic-Metal Systems.
Current edition approved April 1, 2006. Published May 2006. Originally
approved in 1959. Last previous edition approved in 1999 as C448–88 (1999).
DOI: 10.1520/C0448-88R06. Balls meeting the requirements of this paragraph are available from the Mobay
For referenced ASTM standards, visit the ASTM website, www.astm.org, or Corporation, 5601 Eastern Avenue, Baltimore, MD 21224.
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM Suitable instruments are available from: Pacific Scientific Company, Gardner/
Standards volume information, refer to the standard’s Document Summary page on Neotec Instrument Division, 2431 Linden Lane, Silver Spring, MD 20910; and
the ASTM website. 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.
C448 – 88 (2006)
shall be provided for positioning the specimen, with respect to should be as flat and free of orange peel or wavy surface as
the gloss head, so that, for a given orientation, the position of possible. Variations from flatness decrease the accuracy of
the specimen during the final gloss reading may be controlled gloss measurements.
to within ⁄16 in. (1.6 mm) of that during the original gloss 8.2 Six specimens shall be tested for each determination of
reading.
resistance to surface abrasion or resistance to subsurface
abrasion.
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
9. Specimen Preparation
phenolicresinorsimilarmaterialshouldbeplacedovertheopeningwhen
the instrument is not in use. The lenses should be cleaned at regular
9.1 Before making any measurements, wash each specimen
intervals with a soft camel’s-hair brush.
with a soft sponge moistened with a warm 1% solution of
Theblackglossstandardshouldbekeptfreeofscratches,andshouldbe
trisodium phosphate (distilled water not essential) and rinse in
protected by wrapping with a soft cloth when not in use.
warm, running tap water. If, when rinsing, the water gathers in
5.4 Apparatus for Oscillating Specimens —The apparatus
drops on the surface, repeat the washing treatment until the
used for oscillating the specimens during test shall impart to
rinse water spreads evenly. While the specimen is still wet,
nine specimens simultaneously a horizontal circular motion
rinse it with ethyl alcohol. A small stream of alcohol from an
suchthateverypointoneachspecimendescribesacircle ⁄8in.
ordinary chemical wash bottle will suffice for rinsing. Pure
(22.2mm)indiameter.Theapparatusshallbeprovidedwithan
ethyl alcohol is preferable, but if it is not available, ethyl
automatic timing device capable of being preset to within 1 s
alcohol that has been denatured with up to 5% of a noncor-
of the desired time and shall operate at a frequency of 300 6
rosive, highly volatile organic compound such as methyl
3cpm(formachinemanufacturedpriortoJuly1981)or345 6
alcohol may be used. Allow the specimens to air dry in a
3 cpm (for machines manufactured after July 1981). The
vertical position and then place in a desiccator. This will
apparatus shall be operated on a firm and level surface.
prevent damage and moisture absorption of the specimens
5.5 Retaining Rings—The retaining rings shall be con-
whichcanadverselyaffecttheweightvalues.Glossandweight
structed of metal lined with rubber. The inside height and
determinationsshouldbeobtainedwithina15-minperiodafter
3 1
diameter of the rubber-lined ring shall be 1 ⁄16 6 ⁄16 in. (30.2
the specimens have been cleaned and placed in the desiccator.
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
enameled metal specimen to produce a watertight seal. Means
benzene, either alone or in combination with methyl alcohol. If ethyl
shall be provided for introducing an abrasive charge after the
alcohol is not available, isopropyl alcohol or acetone may be used, but
specimen is secured. Nine retaining rings are required.
pure ethyl alcohol is recommended if available. Avoid alcohol denatured
5.6 Buret, of suitable capacity to deliver 20 mL of water at
withaningredientoflowvolatility,whichwillremainasasurfacefilmon
20°C (68°F).
thespecimenwhenusedtorinseitbeforeoraftertreatment.Surfacefilms
may significantly affect gloss readings.
6. Abrasives
10. Resistance to Surface Abrasion of Porcelain Enamels
6.1 For the surface abrasion tests the−70 +100-mesh frac-
Having 45° Specular Gloss of More than 30 Gloss
tion of Pennsylvania-type glass sand, preferably as ground
Units
from quartzite (quartz rock), shall be used. For the subsurface
abrasion test No. 80 grit aluminum oxide abrasive medium
10.1 Marking of Specimens and Determining Initial 45°
shall be used.
Specular Gloss—Mark each specimen so that its orientation
maybecontrolled.Amarkonthebackatoneedgewillsuffice.
7. Reference Standards
Place this edge against the specimen guide on the gloss head
7.1 Specimens of standard calibrated polished plate glass
for the first reading. Then make three other readings, turning
which shows a coefficient of variation no greater than 1.5%
the specimen clockwise through 90° between readings.
when tested for surface abrasion in accordance with the
NOTE 3—The measured gloss of light-transmitting specimens of such
procedure as specified in Section 10, and which meets require-
materials as transparent or translucent glass or plastic may be affected by
ments of Table A1.4 shall be used as reference standards.
light reflected from the back side of the specimen or transmitted through
the specimen from the room. To minimize errors from this source, the
8. Test Specimens
following precautions should be taken:
3 1
8.1 Test specimens shall be 4 ⁄8 6 ⁄4 in. (111.1 6 6.4 mm)
(1) Roughen the back of transparent specimens to eliminate specular
square,andmaybepreparedbyenamelingmetalblanksofthat
reflection from this surface.
size or by cutting a larger piece. Specimens for the weight loss
(2) Cover back and edges of light-transmitting specimens with an
tests should not exceed the capacity of the analytical balance opaque black cloth when measuring gloss to prevent normal room
illumination from being transmitted through the specimen, or light from
selected for obtaining the weights of the specimens. When
the instrument from being reflected back through the specimen from a
gloss measurements are to be made, the specimens tested
light surface in contact with the back of the specimen.This is particularly
important when using a glossmeter with the specimen holder on top.
(3) Put no labels near the center of light-transmitting specimens.
A suitable apparatus is the P.E.I. Abrasion Tester, manufactured by the
Keystone Electric Co., 2807 Annapolis Road, Baltimore, MD 21230.
10.2 Determining Correct Abrasion Time— The correct
These standard materials are available from the Mobay Corp., 5601 Eastern
Ave., Baltimore, MD 21224. abrasion time is the time required to reduce the 45° specular
C448 – 88 (2006)
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 calculatingtheaveragepercentage45°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
NOTE 4—If it is desirable, nine samples may be treated simultaneously,
counts) on machines manufactured after July 1981.
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
Introducing Abrasive Mixture—Center each specimen in one
desired may be used and the arrangement may be such that the number of
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
device for the previously determined time required to reduce
NOTE 5—This check test need not be made each time enameled metal
the 45° specular gloss of a standard plate glass specimen to
specimens are tested.The time between check tests will be determined by
53%. Set the selector switch to the “automatic” position and
the number of tests made by the laboratory.
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:
10.5.1 Clean the sample specimens and equipment as fol-
11.1 Determining Initial Weight of Specimens—Weigh each
lows:
specimen to the nearest 0.1 mg within 15 min after it has been
10.5.1.1 Immediately after treatment, loosen the wing nuts
rinsed with alcohol.
that secure the specimens to the abrasion tester. Carefully
NOTE 6—When weight determinations are to be made, the specimens
removethesamplepanel,retainingringapparatusandabrasive
should be handled with care to prevent chipping, which may introduce
medium as a sealed unit. (Thi
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