ASTM G54-84(1996)
(Practice)Standard Practice for Simple Static Oxidation Testing (Withdrawn 2002)
Standard Practice for Simple Static Oxidation Testing (Withdrawn 2002)
SCOPE
1.1 Purpose -This engineering practice covers determination of preliminary information on the relative growth, scaling, and microstructural characteristics of an oxide on the surface of a pure metal or alloy under isothermal conditions in still air. This test does not necessarily apply to testing of coated specimens.
1.2 Application -This procedure may be applied to any pure metal, alloy, or groups thereof that exhibit the formation of a surface oxide structure in still air at the temperature of interest, usually above about 540°C (1004°F). Direct comparison of material at a constant temperature or the effect of temperature on a given material may be investigated. Oxidation is a dynamic time- and temperature-dependent process. The relative resistances of materials to oxidation at constant temperature should, therefore, be determined over at least three time periods.
1.3 Limitations:
1.3.1 Materials usually exhibit one of several basic reactions to a high-temperature oxidizing environment. They may form a protective oxide layer which protects them indefinitely. They may form a protective oxide layer which persists for some finite time after which "scale breakaway" occurs and a scaling rate develops. They may also form a nonprotective oxide which allows rapid oxygen penetration to the metal and subsequent rapid deterioration by internal oxidation, which may render the material brittle and unusable without much observable surface or mass change. Some oxides may be liquid and thereby flux any protective oxides from the surface. Another reaction may be vaporization of the scale or one or more of the reactants. The correct interpretation of this test is thus dependent upon both mass change and microstructural depth of attack data. One should not be used without the other. For materials that form high vapor pressure oxides one must also collect the vaporized oxide by some method if it is required to complete the material balance. Specific methods to do this are beyond the scope of this practice.
1.3.2 Materials that develop very adherent and protective oxide layers at the test temperature of interest may not be comparable in any practical amount of time because the time to scale breakaway is so long. Some alloys also react very differently to the relatively mild conditions of static oxidation than they do to the cyclic temperatures often found in service where differential thermal expansion may cause accelerated scale breakaway. This general test should thus not be used to predict the quantitative reactions of materials for specific high-temperature applications.
1.4 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.
General Information
Standards Content (Sample)
Designation: G 54 – 84 (Reapproved 1996)
AMERICAN SOCIETY FOR TESTINGAND MATERIALS
100 Barr Harbor Dr., West Conshohocken, PA19428
Reprinted from theAnnual Book ofASTM Standards. CopyrightASTM
Standard Practice for
Simple Static Oxidation Testing
ThisstandardisissuedunderthefixeddesignationG54;thenumberimmediatelyfollowingthedesignationindicatestheyearoforiginal
adoptionor,inthecaseofrevision,theyearoflastrevision.Anumberinparenthesesindicatestheyearoflastreapproval.Asuperscript
epsilon (e) indicates an editorial change since the last revision or reapproval.
1. Scope 1.3.2 Materials that develop very adherent and protective
oxide layers at the test temperature of interest may not be
1.1 Purpose—This engineering practice covers determina-
comparableinanypracticalamountoftimebecausethetimeto
tionofpreliminaryinformationontherelativegrowth,scaling,
scale breakaway is so long. Some alloys also react very
andmicrostructuralcharacteristicsofanoxideonthesurfaceof
differently to the relatively mild conditions of static oxidation
a pure metal or alloy under isothermal conditions in still air.
than they do to the cyclic temperatures often found in service
This test does not necessarily apply to testing of coated
where differential thermal expansion may cause accelerated
specimens.
scale breakaway. This general test should thus not be used to
1.2 Application—This procedure may be applied to any
predict the quantitative reactions of materials for specific
pure metal, alloy, or groups thereof that exhibit the formation
high-temperature applications.
of a surface oxide structure in still air at the temperature of
1.4 This standard does not purport to address all of the
interest, usually above about 540°C (1004°F). Direct compari-
safety concerns, if any, associated with its use. It is the
son of material at a constant temperature or the effect of
responsibility of the user of this standard to establish appro-
temperature on a given material may be investigated. Oxida-
priate safety and health practices and determine the applica-
tion is a dynamic time- and temperature-dependent process.
bility of regulatory limitations prior to use.
The relative resistances of materials to oxidation at constant
temperatureshould,therefore,bedeterminedoveratleastthree
2. Referenced Documents
time periods.
2.1 ASTM Standards:
1.3 Limitations:
E220 Method for Calibration of Thermocouples by Com-
1.3.1 Materials usually exhibit one of several basic reac-
parison Techniques
tions to a high-temperature oxidizing environment. They may
E230 Temperature–Electromotive Force (EMF) Tables for
form a protective oxide layer which protects them indefinitely.
Standardized Thermocouples
They may form a protective oxide layer which persists for
G1 Practice for Preparing, Cleaning, and Evaluating Cor-
some finite time after which “scale breakaway” occurs and a
rosion Test Specimens
scaling rate develops. They may also form a nonprotective
oxide which allows rapid oxygen penetration to the metal and
3. Significance and Use
subsequent rapid deterioration by internal oxidation, which
3.1 Isothermal Conditions:
may render the material brittle and unusable without much
3.1.1 It is virtually impossible to maintain a uniform heat
observablesurfaceormasschange.Someoxidesmaybeliquid
zone in a vertical-tube furnace. An open-tube furnace at high
and thereby flux any protective oxides from the surface.
temperature might be considered to have still air yet variable
Another reaction may be vaporization of the scale or one or
convection currents will exist, also a tube furnace with one
more of the reactants. The correct interpretation of this test is
closedendwillhaveadifferentflowpattern.Finally,erroneous
thus dependent upon both mass change and microstructural
resultsarepossiblewhentestsareconductedonmaterialswith
depthofattackdata.Oneshouldnotbeusedwithouttheother.
volatileorliquidoxidespeciessuchasWO,M O,V O ,etc.
3 0 3 2 5
For materials that form high vapor pressure oxides one must
in low air flow conditions.
also collect the vaporized oxide by some method if it is
required to complete the material balance. Specific methods to
4. Apparatus
do this are beyond the scope of this practice.
4.1 Furnace and Controls:
4.1.1 Furnace, electric-resistance-heated type, capable of
heating still air to the temperature of interest. The furnace
This practice is under the jurisdiction ofASTM Committee G-1 on Corrosion
should be large enough to contain all specimens of a given
of Metals, and is the direct responsibility of Subcommittee G01.05 on Laboratory
study without critical regard for location. A small window in
Corrosion Tests.
Current edition approved Feb. 24, 1984. Published May 1984. Originally
the furnace wall or door through which to view the specimens
published as G54–77. Last previous edition G54–77.
Foradiscussionofoxidevaporizationathightemperatures,seeTedman,Jr.,C.
S., “The Effect of Oxide Volatilization on the Oxidation Kinetics of Cr and Fe-Cr Annual Book of ASTM Standards, Vol 14.03.
Alloys,” Journal of the Electrochemical Society, Vol 113, 1966, pp. 766–768. Annual Book of ASTM Standards, Vol 03.02.
CCOPYRIGHT American Society for Testing and MaterialsOPYRIGHT American Society for Testing and Materials
LLicensed by Information Handling Servicesicensed by Information Handling Services
G54
is helpful. A number of commercia l “box” furnaces are much higher magnifications are usually essential to determine
availablewithinteriordimensionsofabout350by200by120 the fine structure of oxide scales, but this is beyond the scope
mm(14by8by5in.)whichmeetthesecriteria.Theextentand of this test.
location of the constant-temperature zone within the furnace
chamber should be determined for each test temperature. 5. Test Media (Air)
Samples should only be exposed within this zone.
5.1 Humidity—This is usually a function of existing labo-
4.1.2 Thermocouple—A controlling thermocouple compat-
ratory conditions. The oxidation characteristics of some alloy
ible with the temperature being studied appropriately and
types may be affected by humidity variations. It is thus
protected should project into the furnace chamber with its hot
important to include reference standards in each test series or
junction as close as possible to the specimen location. Consult
to expose all materials to be compared at the same time.
Method E220 and Tables E230 for information on thermo-
5.2 Heating Rate—The specimens and their support are
couples.
charged into the furnace operating at the test temperature and
4.1.3 Controls—Test temperature and the precision of its allowed to heat.
control are important to the reproducibility and usefulness of 5.3 Cooling Rate—The specimens and their support are
the results. An indicating controller calibrated for the control removedfromthefurnaceandallowedtocoolinstaticambient
thermocouple and capable of maintaining furnace chamber
air.
temperature is adequate. Within the very general scope of this
procedure, the recommended control precision should be at 6. Preparation of Specimens
least 1% or 610°C (20°F), whichever is smaller. If furnace
6.1 Size—Aspecimen having a total surface of at least 400
2 2
designandthethermocouple’sprecisionallowit,atemperature
mm (0.62 in. ) is recommended insofar as errors in weighing
control precision of 65°C (10°F) is preferred. It may also be
and rounding of corners are a function of specimen size, the
necessary to control the input voltage to the furnace heating
largestconvenientspecimendimensionsaredesirable.Sheetor
elements for the most efficient temperature regulation. Over-
strip specimens are preferred so that edge effects do not mask
temperature controls or continuous temperature recording
normalbehaviorunderexposureconditions.Anyshapemaybe
should be used to guard against inadvertent temperature
used but data obtained from specimens of widely varying
excursions from sticking contacts or thermocouple burnout.
shapesorsizes,andthussurfaceareas,shouldnotbecompared
4.2 Specimen Support:
directly. Duplicate or triplicate specimens should be exposed
4.2.1 Great care must be taken in the selection of this when possible.
material to avoid contamination of the test specimens. Metal 6.2 Method of Cutting—Any practical method of cutting is
suchasplatinum,tungsten,orsomehigh-temperaturealloysis acceptable but sheared edges should be refinished by machin-
acceptable if it has been shown from previous work at the test ing, filing, or abrading to remove the severely disturbed layer
temperature to be nonreactive with the test specimen at points of metal.
of contact. Ceramic materials such as porcelain, Alundum, or 6.3 Preparation of Surfaces—Surface preparation, or lack
fire clay may also be used if they are inert at the exposure
of it, may affect the oxide-forming characteristics of some
temperature. Some ceramics may cause localized, accelerated
materials, particularly under borderline conditions. Particular
corrosion if they contain sulfur, phos
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