ASTM D6559-22

Standard Test Method for Determination of Thermogravimetric (TGA) Air Reactivity of Baked Carbon Anodes and Cathode Blocks

SIGNIFICANCE AND USE
5.1 The air reactivity rates are used to quantify the tendency of a carbon artifact to react with air. Carbon consumed by this unwanted side reaction is unavailable for the primary reactions of reducing alumina to the primary metal. Air reactivity dusting rate is used by some companies to quantify the tendency of the coke aggregate or binder coke of a carbon artifact to selectively react with these gases. Preferential attack of the binder coke or coke aggregate of a carbon artifact by these gases causes some carbon to fall off or dust, making the carbon unavailable for the primary reaction of reducing alumina and, more importantly, reducing the efficiency of the aluminum reduction cell.  
5.2 Comparison of air reactivity and dusting rates is useful in selecting raw materials for the manufacture of commercial anodes for specific smelting technologies in the aluminum reduction industry.  
5.3 Air reactivity rates are used for evaluating effectiveness and beneficiation processes or for research purposes.
SCOPE
1.1 This test method covers the thermogravimetric (TGA) determination of air reactivity and dusting of shaped carbon anodes and cathode blocks used in the aluminum reduction industry. The apparatus selection covers a significant variety of types with various thermal conditions, sample size capability, materials of construction, and procedures for determining the mass loss and subsequent rate of reaction. This test method standardizes the variables of sample shape, reaction temperature, gas velocity over the exposed surfaces, and reaction time such that results obtained on different apparatuses are correlatable.  
1.2 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.  
1.3 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, health, and environmental practices and determine the applicability of regulatory limitations prior to use.  
1.4 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.

General Information

• Status: Published
• Publication Date: 30-Apr-2022
• ICS: 77.020 - Production of metals
• Technical Committee: D02 - Petroleum Products, Liquid Fuels, and Lubricants
• Drafting Committee: D02.05 - Properties of Fuels, Petroleum Coke and Carbon Material

Relations

• Refers: ASTM E691-13 - Standard Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Method
• Effective Date: 01-May-2013
• Refers: ASTM D6354-12 - Standard Guide for Sampling Plan and Core Sampling of Carbon Cathode Blocks Used in Aluminum Production
• Effective Date: 15-Apr-2012
• Refers: ASTM E691-11 - Standard Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Method
• Effective Date: 01-Nov-2011
• Refers: ASTM D6353-06(2011) - Standard Guide for Sampling Plan and Core Sampling for Prebaked Anodes Used in Aluminum Production
• Effective Date: 01-May-2011
• Refers: ASTM D6354-98(2008) - Standard Guide for Sampling Plan and Core Sampling of Carbon Cathode Blocks Used in Aluminum Production
• Effective Date: 15-Oct-2008
• Refers: ASTM E691-08 - Standard Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Method
• Effective Date: 01-Oct-2008
• Refers: ASTM D6353-06 - Standard Guide for Sampling Plan and Core Sampling for Prebaked Anodes Used in Aluminum Production
• Effective Date: 01-Jul-2006
• Refers: ASTM E691-05 - Standard Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Method
• Effective Date: 01-Nov-2005
• Refers: ASTM D6353-98(2003) - Standard Guide for Sampling Plan and Core Sampling for Prebaked Anodes Used in Aluminum Production
• Effective Date: 01-Nov-2003
• Refers: ASTM D6354-98(2003) - Standard Guide for Sampling Plan and Core Sampling of Carbon Cathode Blocks Used in Aluminum Production
• Effective Date: 01-Nov-2003
• Refers: ASTM E691-99 - Standard Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Method
• Effective Date: 10-May-1999
• Refers: ASTM D6354-98 - Standard Guide for Sampling Plan and Core Sampling of Carbon Cathode Blocks Used in Aluminum Production
• Effective Date: 10-Dec-1998
• Refers: ASTM D6353-98 - Standard Guide for Sampling Plan and Core Sampling for Prebaked Anodes Used in Aluminum Production
• Effective Date: 10-Dec-1998

Overview

ASTM D6559-22 is the standard test method issued by ASTM International for the determination of thermogravimetric (TGA) air reactivity and dusting of baked carbon anodes and cathode blocks. These components are critical in the aluminum reduction industry, where they serve as essential parts in the electrolytic smelting process. The standard method provides a uniform approach to evaluating how carbon-based materials used in smelting react to air exposure, specifically the rates of mass loss due to reaction with air and the associated dusting phenomena.

Air reactivity has a direct impact on the efficiency of aluminum production, as unwanted reactions between carbon artifacts and air result in carbon loss, dust generation, and reduced cell performance. ASTM D6559-22 enables manufacturers and researchers to standardize measurements and ensure comparability between different laboratories and production sites.

Key Topics

• Thermogravimetric Air Reactivity: Quantification of carbon mass loss when exposed to air under controlled thermal conditions.
• Dusting Rate: Measurement of the amount of carbon particulate released during testing, which provides insight into material durability and stability.
• Standardized Variables: Control of factors such as sample shape (right cylindrical geometry), reaction temperature, gas velocity, and reaction time to enable reliable, consistent results.
• Precision and Bias: Procedures for repeatability and reproducibility have been established, ensuring reliable interlaboratory comparisons.
• Safety and Units: The standard is presented in SI units and highlights the responsibility of users to adhere to appropriate safety and regulatory standards.

Applications

ASTM D6559-22 is valuable for:

• Aluminum Reduction Industry: Used to assess and select raw materials (anode and cathode blocks) that will exhibit optimal performance and minimal degradation during alumina reduction processes.
• Material Selection: Air reactivity and dusting data guide the selection of cokes and binders that form the carbon anodes and cathodes, helping maximize operational efficiency and output.
• Quality Control and Research: Used for performance benchmarking, quality assurance, and evaluation of beneficiation processes or new material formulations.
• Process Optimization: Supports efforts to enhance the lifespan of carbon artifacts, to minimize loss due to air reactivity, and to lower operational costs by improving the overall efficiency of smelting cells.
• Compliance and Standardization: Assists in ensuring that materials sourced from different suppliers or tested in different locations meet equivalent performance standards, facilitating reliable global trade.

Related Standards

• ASTM D6353 - Guide for Sampling Plan and Core Sampling for Prebaked Anodes Used in Aluminum Production
• ASTM D6354 - Guide for Sampling Plan and Core Sampling of Carbon Cathode Blocks Used in Aluminum Production
• ASTM E691 - Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Method

Practical Value

ASTM D6559-22 provides a standardized, reproducible method for quantifying air reactivity and dusting in carbon anodes and cathode blocks, supporting improved selection, quality control, and research in the aluminum industry. By following this test method, organizations can enhance the performance and reliability of their reduction technology, comply with international best practices, and drive operational improvements through quality materials testing. This standard is particularly important for manufacturers concerned with efficiency and longevity of carbon components in smelting processes.

Key search terms: thermogravimetric air reactivity, carbon anodes, carbon cathode blocks, air reactivity testing, aluminum reduction industry, ASTM D6559-22.

Standards Content (Sample)

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: D6559 − 22
Standard Test Method for
Determination of Thermogravimetric (TGA) Air Reactivity of
Baked Carbon Anodes and Cathode Blocks
This standard is issued under the fixed designation D6559; 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 (´) indicates an editorial change since the last revision or reapproval.
1. Scope* Carbon Cathode Blocks Used in Aluminum Production
E691 Practice for Conducting an Interlaboratory Study to
1.1 This test method covers the thermogravimetric (TGA)
Determine the Precision of a Test Method
determination of air reactivity and dusting of shaped carbon
anodes and cathode blocks used in the aluminum reduction
3. Terminology
industry.The apparatus selection covers a significant variety of
3.1 Definitions of Terms Specific to This Standard:
types with various thermal conditions, sample size capability,
3.1.1 dusting, n—the quantity of carbon that falls off the
materials of construction, and procedures for determining the
carbonartifactwhileinthereactionchamberandiscollectedin
mass loss and subsequent rate of reaction. This test method
a container at the bottom of the reaction chamber plus the
standardizes the variables of sample shape, reaction
quantity of carbon that is collected from the carbon artifact
temperature, gas velocity over the exposed surfaces, and
after cooling (optional).
reactiontimesuchthatresultsobtainedondifferentapparatuses
are correlatable. 3.1.2 final air reactivity, n—the mass loss of the carbon
artifactduringthefinal30 minofexposuretoairinthereaction
1.2 The values stated in SI units are to be regarded as
chamber divided by the initial geometric (right cylindrical)
standard. No other units of measurement are included in this
exposed surface area of the sample, expressed as milligrams
standard.
per centimetre squared per hour.
1.3 This standard does not purport to address all of the
3.1.3 initial air reactivity, n—the mass loss of the carbon
safety concerns, if any, associated with its use. It is the
artifact during the first 30 min of exposure to air in the reaction
responsibility of the user of this standard to establish appro-
chamber divided by the initial geometric (right cylindrical)
priate safety, health, and environmental practices and deter-
exposed surface area of the sample, expressed as milligrams
mine the applicability of regulatory limitations prior to use.
per centimetre squared per hour.
1.4 This international standard was developed in accor-
3.1.4 total air reactivity, n—thetotalmasslossofthecarbon
dance with internationally recognized principles on standard-
artifact(includingdusting)duringthetotaltimethatthesample
ization established in the Decision on Principles for the
is exposed to air (60 min to 210 min) in the reaction chamber
Development of International Standards, Guides and Recom-
divided by the initial geometric (right cylindrical) exposed
mendations issued by the World Trade Organization Technical
surface area of the sample, expressed as milligrams per
Barriers to Trade (TBT) Committee.
centimetre squared per hour.
2. Referenced Documents
4. Summary of Test Method
2.1 ASTM Standards:
4.1 Initial, final, and total air reactivity and dusting are
D6353 Guide for Sampling Plan and Core Sampling for
determined by passing air at flow rates, giving a standard
Prebaked Anodes Used in Aluminum Production
velocity of reactant gas around cylindrically shaped carbon
D6354 Guide for Sampling Plan and Core Sampling of
artifacts under nearly isothermal conditions for a specified
length of time. The reactivity is determined by continuously
This test method is under the jurisdiction of ASTM Committee D02 on monitoring the sample mass loss. The dusting term is deter-
Petroleum Products, Liquid Fuels, and Lubricantsand is the direct responsibility of
mined by collecting and determining the mass of carbon
SubcommitteeD02.05onPropertiesofFuels,PetroleumCokeandCarbonMaterial.
particles that fall off the sample during reaction or collected
CurrenteditionapprovedMay1,2022.PublishedJuly2022.Originallyapproved
ɛ1
from the sample after the heat treatment.
in 2000. Last previous edition approved in 2016 as D6559 – 00a (2016) . DOI:
10.1520/D6559-22.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or 5. Significance and Use
contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
5.1 The air reactivity rates are used to quantify the tendency
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. of a carbon artifact to react with air. Carbon consumed by this
*A Summary of Changes section appears at the end of this standard
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D6559 − 22
unwanted side reaction is unavailable for the primary reactions 6.1.1 Furnace and Controller, capable of maintaining con-
ofreducingaluminatotheprimarymetal.Airreactivitydusting stant temperature within 62 °C in the 100 mm region centered
rate is used by some companies to quantify the tendency of the on the specimen. The example apparatus of Fig. 1 employs a
cokeaggregateorbindercokeofacarbonartifacttoselectively three zone heating element and associated controls to accom-
react with these gases. Preferential attack of the binder coke or plish this, but other methods such as tapered windings or long
coke aggregate of a carbon artifact by these gases causes some linear heaters are also suitable. The control thermocouple is a
carbon to fall off or dust, making the carbon unavailable for the groundedtypeandshallbelocatedwithinthereactionchamber
primary reaction of reducing alumina and, more importantly, near the surface of the test sample to allow the furnace
reducing the efficiency of the aluminum reduction cell. controller to adjust to the exothermic reaction that occurs
during the air reactivity test.The control thermocouple shall be
5.2 Comparison of air reactivity and dusting rates is useful
positioned 4 mm 6 1 mm from the side sample surface and
in selecting raw materials for the manufacture of commercial
centeredverticallywithin5 mmofthecenter.Thefurnaceshall
anodes for specific smelting technologies in the aluminum
be large enough to accept the reaction chamber.
reduction industry.
6.1.2 Reaction Chamber, consisting of a vertical tube con-
5.3 Air reactivity rates are used for evaluating effectiveness
structed of a material capable of withstanding the temperature
and beneficiation processes or for research purposes.
ofthereactionwithsufficientinsidediameter(ID)toacceptthe
sample and sample holder while not affecting the gas flow to
6. Apparatus
and from the sample (100 mm 6 25 mm ID is recommended).
6.1 The apparatus to be used should be as simple as possible The reaction chamber is to be constructed with a dust collec-
andbecommensuratewithwhatistobeachieved,theprincipal tion cup at the bottom, which is removable and capable of
criteria being that the reaction rate is to be determined under capturing all the dust that falls off the sample during the test.
isothermal conditions and unaffected by physical and chemical The most common materials of construction are quartz and
properties inherent to the apparatus (such as gas diffusion Inconel.
patterns, gas temperature, exposed sample surface area, and so 6.1.3 Sample Holders, capable of supporting the sample in
forth).Atypical apparatus that has been found to be suitable is the reaction chamber for the duration of the test and should be
illustrated in Fig. 1. capable of being reusable. The sample holder shall not change
FIG. 1 Typical Air Reactivity Apparatus
D6559 − 22
in mass during the test, affect the diffusion pattern of the gases 6.1.10 Calipers, or other suitable device, capable of mea-
to or from the sample, limit the gas accessible surface area of suring to within 0.01 mm for determining the sample diameter
the test sample, or interfere with the free fall of dust from the and height to calculate geometric surface area exposed to the
sample. A typical sample holder is illustrated in Fig. 2. test gases.
6.1.11 Optional Equipment, including but not limited to,
6.1.4 Gas Preheat Tube, extending into the first heat zone of
automatic control devices, multichannel line selector, and
the reaction chamber to preheat the gases prior to entering the
personal computer to automate data gathering, manipulation,
reaction chamber.The length and diameter of the tube can vary
reporting, and storage.
as long as the gases exiting the tube are the same temperature
as the reaction chamber. The inlet gas shall exit the preheat
7. Reagents
tube downward to prevent channeling of the gas through the
reaction chamber and to prevent plugging of the preheat tube 7.1 Purity of Reagents—Reagent grade conforming to the
with carbon dust. specifications of the Committee on Analytical Reagents of the
American Chemical Society.
6.1.5 Balance, capable of measuring the weight of the
7.1.1 Nitrogen—99.95 %.
sample and sample holder (approximately 200 g maximum)
7.1.2 Air—less than 0.1 % moisture.
continuously throughout the duration of the test to the nearest
0.01 g.
8. Sampling
6.1.6 Gas Flow Meter, capable of monitoring the gas flow
8.1 Shape the carbon specimen by coring and cutting or
rate into the reaction chamber. All gas flow rates are to be
machining to a right cylindrical geometry, with a length in the
maintained at the rate determined for the particular test
range 25 mm 6 1.0 mm to 50 mm 6 1.0 mm and a diameter in
apparatus.
the range 20 mm 6 1.0 mm to 50 mm 6 1.0 mm. Most sample
6.1.7 Needle Valve, to make fine adjustments to the gas flow
holders require a hole of about 3 mm diameter to be drilled
rate.
vertically through the center of the cylinder to accommodate a
6.1.8 Pressure Reducing Valve, to reduce the pressure of the
hanger. The shaped specimen is to be smooth and free of
compressed gases to near atmospheric pressure prior to ent
...

This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
´1
Designation: D6559 − 00a (Reapproved 2016) D6559 − 22
Standard Test Method for
Determination of Thermogravimetric (TGA) Air Reactivity of
Baked Carbon Anodes and Cathode Blocks
This standard is issued under the fixed designation D6559; 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 (´) indicates an editorial change since the last revision or reapproval.
ε NOTE—SI units formatting was corrected editorially in May 2016.
1. Scope Scope*
1.1 This test method covers the thermogravimetric (TGA) determination of air reactivity and dusting of shaped carbon anodes and
cathode blocks used in the aluminum reduction industry. The apparatus selection covers a significant variety of types with various
thermal conditions, sample size capability, materials of construction, and procedures for determining the mass loss and subsequent
rate of reaction. This test method standardizes the variables of sample dimensions,shape, reaction temperature, gas velocity over
the exposed surfaces, and reaction time such that results obtained on different apparatuses are correlatable.
1.2 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
1.3 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 safety, health, and healthenvironmental practices and determine the
applicability of regulatory limitations prior to use.
1.4 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.
2. Referenced Documents
2.1 ASTM Standards:
D6353 Guide for Sampling Plan and Core Sampling for Prebaked Anodes Used in Aluminum Production
D6354 Guide for Sampling Plan and Core Sampling of Carbon Cathode Blocks Used in Aluminum Production
E691 Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Method
3. Terminology
3.1 Definitions of Terms Specific to This Standard:
3.1.1 dusting, n—the quantity of carbon that falls off the carbon artifact while in the reaction chamber and is collected in thea
container at the bottom of the reaction chamber.chamber plus the quantity of carbon that is collected from the carbon artifact after
cooling (optional).
This test method is under the jurisdiction of ASTM Committee D02 on Petroleum Products, Liquid Fuels, and Lubricantsand is the direct responsibility of Subcommittee
D02.05 on Properties of Fuels, Petroleum Coke and Carbon Material.
Current edition approved April 1, 2016May 1, 2022. Published May 2016July 2022. Originally approved in 2000. Last previous edition approved in 20102016 as
ɛ1
D6559 – 00a (2010).(2016) . DOI: 10.1520/D6559-00AR16E01.10.1520/D6559-22.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
*A Summary of Changes section appears at the end of this standard
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D6559 − 22
3.1.2 final air reactivity, n—the mass loss of the carbon artifact during the final 30 min of exposure to air in the reaction chamber
divided by the initial geometric (right cylindrical) exposed surface area of the sample, expressed as milligrams per centimetre
squared per hour.
3.1.3 initial air reactivity, n—the mass loss of the carbon artifact during the first 30 min of exposure to air in the reaction chamber
divided by the initial geometric (right cylindrical) exposed surface area of the sample, expressed as milligrams per centimetre
squared per hour.
3.1.4 total air reactivity, n—the total mass loss of the carbon artifact (including dusting) during the total time that the sample is
exposed to air (180 min) (60 min to 210 min) in the reaction chamber divided by the initial geometric (right cylindrical) exposed
surface area of the sample, expressed as milligrams per centimetre squared per hour.
4. Summary of Test Method
4.1 Initial, final, and total air reactivity and dusting are determined by passing air at flow rates, giving a standard velocity of
reactant gas around cylindrically shaped carbon artifacts under nearly isothermal conditions for a specified length of time. The
reactivity is determined by continuously monitoring the sample mass loss. The dusting term is determined by collecting and
determining the mass of carbon particles that fall off the sample during reaction.reaction or collected from the sample after the heat
treatment.
5. Significance and Use
5.1 The air reactivity rates are used to quantify the tendency of a carbon artifact to react with air. Carbon consumed by this
unwanted side reaction is unavailable for the primary reactions of reducing alumina to the primary metal. Air reactivity dusting
rate is used by some companies to quantify the tendency of the coke aggregate or binder coke of a carbon artifact to selectively
react with these gases. Preferential attack of the binder coke or coke aggregate of a carbon artifact by these gases causes some
carbon to fall off or dust, making the carbon unavailable for the primary reaction of reducing alumina and, more importantly,
reducing the efficiency of the aluminum reduction cell.
5.2 Comparison of air reactivity and dusting rates is useful in selecting raw materials for the manufacture of commercial anodes
for specific smelting technologies in the aluminum reduction industry.
5.3 Air reactivity rates are used for evaluating effectiveness and beneficiation processes or for research purposes.
6. Apparatus
6.1 The apparatus to be used should be as simple as possible and be commensurate with what is to be achieved, the principal
criteria being that the reaction rate is to be determined under isothermal conditions and unaffected by physical and chemical
properties inherent to the apparatus (such as gas diffusion patterns, gas temperature, exposed sample surface area, and so forth).
A typical apparatus that has been found to be suitable is illustrated in Fig. 1.
6.1.1 Furnace and Controller, capable of maintaining constant temperature within 62 °C in the 100 mm region centered on the
specimen. The example apparatus of Fig. 1 employs a three zone heating element and associated controls to accomplish this, but
other methods such as tapered windings or long linear heaters are also suitable. The control thermocouple is a grounded type and
shall be located within the reaction chamber near the surface of the test sample to allow the furnace controller to adjust to the
exothermic reaction that occurs during the air reactivity test. The control thermocouple shall be positioned 4 mm 6 1 mm from
the side sample surface and centered vertically within 5 mm of the center. The furnace shall be large enough to accept the reaction
chamber.
6.1.2 Reaction Chamber, consisting of a vertical tube constructed of a material capable of withstanding the temperature of the
reaction with sufficient inside diameter (ID) to accept the sample and sample holder while not affecting the gas flow to and from
the sample (100 mm 6 25 mm ID is recommended). The reaction chamber is to be constructed with a dust collection cup at the
bottom, which is removable and capable of capturing all the dust that falls off the sample during the test. The most common
materials of construction are quartz and Inconel.
6.1.3 Sample Holders, capable of supporting the sample in the reaction chamber for the duration of the test and should be capable
D6559 − 22
FIG. 1 Typical Air Reactivity Apparatus
of being reusable. The sample holder shall not change in mass during the test, affect the diffusion pattern of the gases to or from
the sample, limit the gas accessible surface area of the test sample, or interfere with the free fall of dust from the sample. A typical
sample holder is illustrated in Fig. 2.
FIG. 2 Typical Sample Holder
D6559 − 22
6.1.4 Gas Preheat Tube, extending into the first heat zone of the reaction chamber to preheat the gases prior to entering the reaction
chamber. The length and diameter of the tube can vary as long as the gases exiting the tube are the same temperature as the reaction
chamber. The inlet gas shall exit the preheat tube downward to prevent channeling of the gas through the reaction chamber and
to prevent plugging of the preheat tube with carbon dust.
6.1.5 Balance, capable of measuring the weight of the sample and sample holder (approximately 200 g maximum) continuously
throughout the duration of the test to the nearest 0.01 g.
6.1.6 Gas Flow Meter, capable of monitoring the gas flow rate into the reaction chamber. All gas flow rates are to be maintained
at the rate determined for the particular test apparatus.
6.1.7 Needle Valve, to make fine adjustments to the gas flow rate.
6.1.8 Pressure Reducing Valve, to reduce the pressure of the compressed gases to near atmospheric pressure prior to entering the
gas flow meter through the needle valve.
6.1.9 Thermocouple(s), inserted into the reaction chamber to calibrate the furnace zone controllers. An optional thermocouple may
be used to monitor reaction temperatures. Some users find continuous temperature measurement of the internal reaction chamber
to be of value.
6.1.10 Calipers, or other suitable device, capable of measuring to within 0.01 mm for determining the sample diameter and height
to calculate geometric surface area exposed to the test gases.
6.1.11 Optional Equipment, including but not limited to, automatic control devices, multichannel line selector, and personal
computer to automate data gathering, manipulation, reporting, and storage.
7. Reagents
7.1 Purity of Reagents—Reagent grade conforming to the specifications of the Committee on Analytical Reagents of the American
Chemical Society.
7.1.1 Nitrogen—99.95 %.
7.1.2 Air—less than 0.1 % moisture.
8. Sampling
8.1 Shape the carbon specimen by coring and cutting or machining to a right cylindrical geometry, with a length in the range
25 mm 6 1.0 mm to 50 mm 6 1.0 mm in length and 50 mm 6 1.0 mm in diameter. and a diameter in the range 20 mm 6 1.0 mm
to 50 mm 6 1.0 mm. Most sample holders require a hole of about 3 mm diameter to be drilled vertically through the center of the
cylinder to accommodate a hanger. The shaped specimen is to be smooth and free of visible cracks and gouges. Sampling plans
for anodes and cathode blocks given in Guides D6353 and D6354 may be used if desired.used.
8.2 Dry the shaped specimen in an oven at 105 °C 6 5 °C to constant weight.
8.3 The sample shall be made free of loose carbon dust and impurities from the shaping process by blowing with dry air.
9. Calibration
9.1 The purpose of this procedure is to establish a relationship between the controller settings for three zone furnaces and the
actual temperatures inside the reaction chamber in the region of the specimen. The length to be calibrated is a 100 mm (4 in.) zone.
NOTE 1—For single zone furnaces, the calibration probe shall be placed in center of where sample will be placed and confirm that the 100 mm zone is
within 62 °C.
9.1.1 Insert a multiprobe thermocouple (for example, three couples in same sheath with probes located at the tip and at 50 mm
D655
...