ASTM D6120-97(2002)

An American National Standard
Designation: D 6120 – 97 (Reapproved 2002)
Standard Test Method for
Electrical Resistivity of Anode and Cathode Carbon Material
at Room Temperature
This standard is issued under the fixed designation D 6120; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (e) indicates an editorial change since the last revision or reapproval.
1. Scope 4.2 This test method are used to determine electrical resis-
tivity for various carbon materials typically found in the
1.1 This test method covers the determination of the elec-
aluminum industry. Electrical resistivity of other carbon arti-
trical resistivity at room temperature of solid cylindrical
facts such as graphite and specialty carbons is more appropri-
specimens cored from commercial sized carbon anodes and
ately determined by Test Method C 611.
cathodes. This test method also applies to samples from carbon
blocks prepared in a laboratory.
5. Significance and Use
1.2 This standard does not purport to address all of the
5.1 The electrical resistivity of anode and cathode carbon
safety concerns, if any, associated with its use. It is the
material is important for efficient aluminum cell operation. It is
responsibility of the user of this standard to establish appro-
a quality parameter that determines the suitability of an
priate safety and health practices and determine the applica-
anode/cathode for operation in an aluminum cell.
bility of regulatory limitation prior to use. For specific safety
5.2 The electrical resitivity may be selected as a require-
information, see 8.2.3.
ment in a customer specification.
2. Referenced Documents
6. Apparatus
2.1 ASTM Standards:
6.1 Specimen Holder (Fig. 1), a device for holding a
C 611 Test Method for Electrical Resistivity of Manufac-
2 specimen of 50 mm diameter and a minimum of 120 mm in
tured Carbon and Graphite Articles at Room Temperature
length between two flat copper plates. One of the plates is
D 5502 Test Method for Apparent Density by Physical
swivel mounted to ensure good contact in case the ends of the
Measurements of Manufactured Anode and Cathode Car-
specimen are not perfectly parallel. The plates shall be as large
bon Used by the Aluminum Industry
as the ends of the specimen and electrically insulated from each
3. Terminology other.
6.1.1 Voltage Drop Contact Points—The contact points
3.1 Definitions:
shall be conical or knife edge in shape and securely fastened to
3.1.1 electrical resistivity, n—the electrical resistance of-
rigid insulatig material with a minimum spacing of 50 mm and
fered by a material to the flow of current, times the cross-
a maximum spacing of 80 % of the length of the specimen. The
sectional area of current flow and per unit length of current
distance (L) in millimetres (mm) betweeen the center of the
path, the reciprocal of conductivity. It is also known as
4 conical points or knife edges is used when calculating the
resistivity, or specific resistance.
electrical resistivity.
4. Summary of Test Method 6.2 Apparatus for Indirect Resistance Measurement (per-
mits measurement of voltage and current needed for calculat-
4.1 An electrical current is passed through a carbon cylinder
ing electrical resistivity):
and the voltage drop or electrical resistance is measured
6.2.1 dc Power Supply—The power supply shall be capable
between two points along its length. The resistivity is calcu-
of supplying a minimum DC current of 10 amps at an electrical
lated based on the voltage drop or electrical resistance, distance
potential of up to 5 V. The line and load regulation shall be less
between the two points, and the cross-sectional area of the
than 0.1 % and background noise less than or equal to 0.1 %.
cylinder.
6.2.2 dc Voltage Measuring Instrument, high-impedance
1 device capable of measuring a minimum of 5 V to 0.01 mV.
This test method is under the jurisdiction of ASTM Committee D02 on
Petroleum Products and Lubricantsand is the direct responsibility of Subcommittee 6.2.3 dc Current Measuring Device, a device capable of
D02.05on Properties of Fuels, Petroleum Coke and Oil Shale.
measuring a current of 10 to 0.01 A.
Current edition approved April 10, 1997. Published June 1997.
6.3 Apparatus for Direct Resistance Measurement:
Annual Book of ASTM Standards, Vol 15.01
6.3.1 Electrical Resistance Measuring Device—A device
Annual Book of ASTM Standards, Vol 05.03
Parker, Sybil P., Ed in Chief, Dictionary of Scientific and Technical Terms,
capable of measuring electrical resistance directly to
McGraw Hill Book Co., Fourth Ed., 1989, p 615.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
D 6120
a 45° angle. Make sure contacts are still longitudinally centered
and take a voltage reading. Continue moving in the same
direction around the circumference until a total of eight equally
spaced voltage readings are recorded. (Warning—Passing a
current through a test specimen for an extended period of time
can increase the temperature and consequently lower the
resistance of the specimen.)
8.3 Direct Resistance Measurement:
8.3.1 Mount the test specimen in the holder and tighten
contact plates firmly to the ends of the specimen.
8.3.2 Center the contact points longitudinally on top of the
specimen and measure the resistance. Move the contact points
around the circumference of the cyinder a distance equivalent
to an arc length of the circumference subtended by 45° angle.
Make sure contacts are still longitudinally centered and take a
resistance reading. Continue moving in the same direction
around the circumference until a total of eight equally spaced
FIG. 1 Schematic of Specimen Holder
resistance readings are recorded.
NOTE 2—The current in the specimen when using a direct reading
0.01 milliohms such as a Kelvin bridge or a Micro-ohmmeter.
electrical resistance measuring device (such as a Micro-ohmmeter) is
These devices utilize 4–wire connections (current and voltage)
lower than when using an indirect resistance measurement device (about
and should not be confused with a v
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