ASTM B827-05(2014)

Standard Practice for Conducting Mixed Flowing Gas (MFG) Environmental Tests

SIGNIFICANCE AND USE
4.1 Mixed flowing gas (MFG) tests are used to simulate or amplify exposure to environmental conditions which electrical contacts or connectors can be expected to experience in various application environments (1, 2).4  
4.2 Test samples which have been exposed to MFG tests have ranged from bare metal surfaces, to electrical connectors, and to complete assemblies.  
4.3 The specific test conditions are usually chosen so as to simulate, in the test laboratory, the effects of certain representative field environments or environmental severity levels on standard metallic surfaces, such as copper and silver coupons or porous gold platings (1, 2).  
4.4 Because MFG tests are simulations, both the test conditions and the degradation reactions (chemical reaction rate, composition of reaction products, etc.) may not always resemble those found in the service environment of the product being tested in the MFG test. A guide to the selection of simulation conditions suitable for a variety of environments is found in Guide B845.  
4.5 The MFG exposures are generally used in conjunction with procedures which evaluate contact or connector electrical performance such as measurement of electrical contact resistance before and after MFG exposure.  
4.6 The MFG tests are useful for connector systems whose contact surfaces are plated or clad with gold or other precious metal finishes. For such surfaces, environmentally produced failures are often due to high resistance or intermittences caused by the formation of insulating contamination in the contact region. This contamination, in the form of films and hard particles, is generally the result of pore corrosion and corrosion product migration or tarnish creepage from pores in the precious metal coating and from unplated base metal boundaries, if present.  
4.7 The MFG exposures can be used to evaluate novel electrical contact metallization for susceptibility to degradation due to environmental exposure to the test corrosive gases...
SCOPE
1.1 This practice provides procedures for conducting environmental tests involving exposures to controlled quantities of corrosive gas mixtures.  
1.2 This practice provides for the required equipment and methods for gas, temperature, and humidity control which enable tests to be conducted in a reproducible manner. Reproducibility is measured through the use of control coupons whose corrosion films are evaluated by mass gain, coulometry, or by various electron and X-ray beam analysis techniques. Reproducibility can also be measured by in situ corrosion rate monitors using electrical resistance or mass/frequency change methods.  
1.3 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.  
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 become familiar with all hazards including those identified in the appropriate Material Safety Data Sheet (MSDS) for this product/material as provided by the manufacturer, to establish appropriate safety and health practices, and determine the applicability of regulatory limitations prior to use. See 5.1.2.4.

General Information

• Status: Historical
• Publication Date: 30-Sep-2014
• ICS: 71.100.20 - Gases for industrial application
• Technical Committee: B02 - Nonferrous Metals and Alloys
• Drafting Committee: B02.11 - Electrical Contact Test Methods

Relations

• Replaces: ASTM B827-05(2009)e2 - Standard Practice for Conducting Mixed Flowing Gas (MFG) Environmental Tests
• Effective Date: 01-Oct-2014
• Referred By: ASTM B826-09(2020) - Standard Test Method for Monitoring Atmospheric Corrosion Tests by Electrical Resistance Probes
• Effective Date: 01-Oct-2014
• Referred By: ASTM B845-97(2018) - Standard Guide for Mixed Flowing Gas (MFG) Tests for Electrical Contacts
• Effective Date: 01-Oct-2014
• Referred By: ASTM B825-19 - Standard Test Method for Coulometric Reduction of Surface Films on Metallic Test Samples
• Effective Date: 01-Oct-2014
• Referred By: ASTM B867-95(2018) - Standard Specification for Electrodeposited Coatings of Palladium-Nickel for Engineering Use
• Effective Date: 01-Oct-2014
• Referred By: ASTM B942-21 - Standard Guide for Specification and Quality Assurance for the Electrical Contact Performance of Crimped Wire Terminations
• Effective Date: 01-Oct-2014

Standards Content (Sample)

NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Contact ASTM International (www.astm.org) for the latest information
Designation: B827 − 05 (Reapproved 2014)
Standard Practice for
Conducting Mixed Flowing Gas (MFG) Environmental Tests
This standard is issued under the fixed designation B827; 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 B810TestMethodforCalibrationofAtmosphericCorrosion
Test Chambers by Change in Mass of Copper Coupons
1.1 This practice provides procedures for conducting envi-
B825Test Method for Coulometric Reduction of Surface
ronmental tests involving exposures to controlled quantities of
Films on Metallic Test Samples
corrosive gas mixtures.
B826Test Method for Monitoring Atmospheric Corrosion
1.2 This practice provides for the required equipment and
Tests by Electrical Resistance Probes
methods for gas, temperature, and humidity control which
B845Guide for Mixed Flowing Gas (MFG) Tests for Elec-
enable tests to be conducted in a reproducible manner. Repro-
trical Contacts
ducibility is measured through the use of control coupons
D1193Specification for Reagent Water
whosecorrosionfilmsareevaluatedbymassgain,coulometry,
D2912Test Method for Oxidant Content of theAtmosphere
or by various electron and X-ray beam analysis techniques. 3
(Neutral Ki) (Withdrawn 1990)
Reproducibility can also be measured by in situ corrosion rate
D2914Test Methods for Sulfur Dioxide Content of the
monitors using electrical resistance or mass/frequency change
Atmosphere (West-Gaeke Method)
methods.
D3449Test Method for Sulfur Dioxide in WorkplaceAtmo-
1.3 The values stated in SI units are to be regarded as spheres (Barium Perchlorate Method) (Withdrawn 1989)
D3464Test Method forAverage Velocity in a Duct Using a
standard. No other units of measurement are included in this
standard. Thermal Anemometer
D3609Practice for Calibration Techniques Using Perme-
1.4 This standard does not purport to address all of the
ation Tubes
safety concerns, if any, associated with its use. It is the
D3824Test Methods for Continuous Measurement of Ox-
responsibility of the user of this standard to become familiar
idesofNitrogenintheAmbientorWorkplaceAtmosphere
with all hazards including those identified in the appropriate
by the Chemiluminescent Method
Material Safety Data Sheet (MSDS) for this product/material
D4230Test Method of Measuring Humidity with Cooled-
as provided by the manufacturer, to establish appropriate
Surface Condensation (Dew-Point) Hygrometer
safety and health practices, and determine the applicability of
E902Practice for Checking the Operating Characteristics of
regulatory limitations prior to use. See 5.1.2.4.
X-Ray Photoelectron Spectrometers (Withdrawn 2011)
G91Practice for Monitoring Atmospheric SO Deposition
2. Referenced Documents
Rate for Atmospheric Corrosivity Evaluation
2.1 ASTM Standards:
B542Terminology Relating to Electrical Contacts andTheir
3. Terminology
Use
3.1 Definitions relating to electrical contacts are in accor-
B765GuideforSelectionofPorosityandGrossDefectTests
dance with Terminology B542.
for Electrodeposits and Related Metallic Coatings
B808TestMethodforMonitoringofAtmosphericCorrosion
4. Significance and Use
Chambers by Quartz Crystal Microbalances
4.1 Mixed flowing gas (MFG) tests are used to simulate or
amplify exposure to environmental conditions which electrical
ThispracticeisunderthejurisdictionofASTMCommitteeB02onNonferrous
contactsorconnectorscanbeexpectedtoexperienceinvarious
Metals and Alloys and is the direct responsibility of Subcommittee B02.11 on
application environments (1, 2).
Electrical Contact Test Methods.
Current edition approved Oct. 1, 2014. Published October 2014. Originally
ε2
approved in 1992. Last previous edition approved in 2009 as B827–05 (2009) .
DOI: 10.1520/B0827-05R14.
2 3
For referenced ASTM standards, visit the ASTM website, www.astm.org, or The last approved version of this historical standard is referenced on
contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM www.astm.org.
Standards volume information, refer to the standard’s Document Summary page on Theboldfacenumbersinparenthesesrefertothelistofreferencesattheendof
the ASTM website. this standard.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
B827 − 05 (2014)
4.2 Test samples which have been exposed to MFG tests space accordance with 7.3, with a means to introduce and
have ranged from bare metal surfaces, to electrical connectors, exhaust gases from the chamber.
and to complete assemblies.
5.1.1.2 The chamber isolates the reactive gases from the
external environment. Chamber materials that are not low-
4.3 The specific test conditions are usually chosen so as to
absorbing can affect test conditions by absorbing or emitting
simulate, in the test laboratory, the effects of certain represen-
reactivegases,leadingtocontrolandreproducibilityproblems.
tative field environments or environmental severity levels on
Thechamberconstructionshallbesuchthattheleakrateisless
standard metallic surfaces, such as copper and silver coupons
than 3% of the volume exchange rate.
or porous gold platings (1, 2).
5.1.1.3 The chamber shall have provision for maintaining
4.4 Because MFG tests are simulations, both the test con-
uniformity of the average gas flow velocity within 620%ofa
ditions and the degradation reactions (chemical reaction rate,
specifiedvalueorofthechamberaveragewhenthechamberis
composition of reaction products, etc.) may not always re-
empty. For chambers with a dimension of more than 0.5 m,
semble those found in the service environment of the product
measurement points shall be in accordance with Test Method
being tested in the MFG test. A guide to the selection of
B810. For chambers with all dimensions of less than 0.5 m, a
simulation conditions suitable for a variety of environments is
minimum of five points shall be measured at locations in the
found in Guide B845.
plane of sample exposure (perpendicular to the expected flow
4.5 The MFG exposures are generally used in conjunction
direction) that are equidistant from each other and the walls of
with procedures which evaluate contact or connector electrical thechamber.Afterallfiveormoredatavaluesarerecorded,all
performance such as measurement of electrical contact resis-
measurements shall be repeated a second time. After the two
tance before and after MFG exposure. setsofmeasurementsarerecorded,athirdcompletesetshallbe
recorded. The arithmetic average of the 15 or more measure-
4.6 The MFG tests are useful for connector systems whose
ments shall be the chamber average. See7.5 and 7.6.8.Ifahot
contact surfaces are plated or clad with gold or other precious
wire anemometer is used for gas velocity measurements, it
metal finishes. For such surfaces, environmentally produced
shallbemadeinaccordancewithTestMethodD3464,withthe
failures are often due to high resistance or intermittences
exception that sample sites shall be in accordance with Test
caused by the formation of insulating contamination in the
Method B810.
contact region. This contamination, in the form of films and
5.1.1.4 A sample access port is desirable. This should be
hard particles, is generally the result of pore corrosion and
designedsuchthatcontrolcouponscanberemovedorreplaced
corrosion product migration or tarnish creepage from pores in
without interrupting the flow of gases. Corrosion test chamber
the precious metal coating and from unplated base metal
corrosion rates have been shown to be a function of the
boundaries, if present.
presenceorabsenceoflight (3, 4).Provisionforcontrollingthe
4.7 The MFG exposures can be used to evaluate novel
test illumination level in accordance with a test specification
electricalcontactmetallizationforsusceptibilitytodegradation
shall be made.
due to environmental exposure to the test corrosive gases.
5.1.1.5 Examples of test chamber systems are diagrammed
4.8 The MFG exposures can be used to evaluate the
inFigs.1-3.Theyarenottobeconsideredexclusiveexamples.
shielding capability of connector housings which may act as a
5.1.2 Gas Supply System:
barrier to the ingress of corrosive gases.
5.1.2.1 Description and Requirements—Thegassupplysys-
tem consists of five main parts: a source of clean, dry, filtered
4.9 The MFG exposures can be used to evaluate the
air; a humidity source; corrosive gas source(s); gas delivery
susceptibility of other connector materials such as plastic
system; and corrosive gas concentration monitoring system(s).
housings to degradation from the test corrosive gases.
Totalsupplycapacitymustbesuchastomeetrequirementsfor
4.10 TheMFGtestsarenotnormallyusedasporositytests.
controlofgasconcentrations.Theminimumnumberofvolume
For a guide to porosity testing, see Guide B765.
changes is determined by the requirement that the concentra-
4.11 The MFG tests are generally not applicable where the
tion of corrosive gases be maintained within 615% between
failuremechanismisotherthanpollutantgascorrosionsuchas
gas inlet and outlet.This is verified by measurement of the gas
in tin-coated separable contacts.
concentrations near the gas inlet upstream of the usable
chamber working volume and comparing with gas concentra-
5. Apparatus
tions measured downstream of the usable chamber working
volumejustpriortothechamberexhaust;thesevaluesshallbe
5.1 Apparatus required to conduct MFG tests are divided
within 615% (see 7.6).Alternative methods of demonstrating
into four major categories, corrosion test chamber, gas supply
compliance with the maximum allowable concentration gradi-
system, chamber monitoring system, and chamber operating
ent are acceptable. Normally, a conditioned chamber equili-
system.
brateswithinseveralhoursaftersampleloadingandstartofthe
5.1.1 Corrosion Test Chamber:
corrosivegassupply.Timeslongerthan2hshallbereportedin
5.1.1.1 The chamber shall consist of an enclosure made of
the test report; see Section 8. A guide to estimating supply
nonreactive, low-absorbing, nonmetallic materials contained
requirements is provided in Appendix X1.
within a cabinet or oven capable of maintaining the tempera-
ture to a maximum tolerance of 61°C with a preferred
NOTE 1—Guidance: when inlet to outlet concentrations vary by more
tolerance held to 60.5°C within the usable chamber working than 615%, it usually indicates an overloaded chamber.
B827 − 05 (2014)
(PEL). However, concentrations in the compressed gas cylin-
ders or permeation devices are often above the PEL, and may
exceed the immediately dangerous to life and health level
(IDHL).Thispracticedoesnotaddresssafetyissuesassociated
with MFG testing.)
5.1.2.5 Gas Delivery System—The gas delivery system is
comprised of three main parts: gas supply lines, gas control
valves and flow controllers, and a mixing chamber. The gas
delivery system shall be capable of delivering gases at the
required concentrations and rates within the test chamber.
(1)Allmaterialsusedforthegastransportsystemmustnot
interact with the gases to the extent that chamber gas concen-
trations are affected.
(2)Gases, make-up air, and water vapor must be thor-
oughly mixed before gas delivery to the samples under test in
the chambers. Care must be taken to ensure absence of aerosol
formationinthemixingchamberwherebygasesareconsumed
in the formation of particulates which may interfere with gas
concentration control and may introduce corrosion processes
whicharenotrepresentativeofgaseouscorrosionmechanisms.
Aerosolformationmaybedetectedbythepresenceofavisible
film or deposit on the interior surface of the gas system where
the gases are mixed.
(3)Any fogging of the tubing walls or mixing chamber
walls can be taken to be an indication of a loss of corrosive
gasesfromtheatmosphere.Finalmixingofthespecifiedgases
should occur inside a separate area of, or as close as possible
FIG. 1 Schematic Flow-Through Mixed Flowing Gas (MFG) Test
to, the test chamber so as to ensure thermal equilibration with
System
the test chamber.
(4)Flow measurement capability is required at the inlet of
5.1.2.2 Clean, Dry, Filtered Air Source—Gases other than
the chamber and also at the exhaust of negative pressure
oxygen and nitrogen that are present in the dry air source shall
chambers to ensure the absence of uncalibrated gas streams.
be less than or equal to those defined by OHSAClass D limits
5.1.2.6 Corrosive Gas Concentration Monitoring System—
with the following additional constraint. Gases other than
Standard measurement systems for very low level gas concen-
nitrogen, oxygen, carbon dioxide, noble gases, methane, ni-
trations are listed in Table 1, which provides for gases in
trous oxide, and hydrogen shall be less than 0.005 (ppm) by
common use in present mixed flowing gas systems, for testing
volumetotalandshallbeHighEfficiencyParticulateArrestants
electrical contact performance.
(HEPA) filtered.
(1)Each instrument must be characterized for interference
5.1.2.3 Humidity Source—The humidity source shall use
with the gases specified, both individually and mixed.
distilled or deionized water, Specification D1193,Type1or
(2)Depending on the exact equipment set used, it may not
better, and shall introduce no extraneous material. The humid-
be possible to accurately measure the concentration of some
ity source shall be maintained equivalent to Specification
gases, such as chlorine, in combination with any of the other
D1193 Type II or better, with the exception that electrical
gases.
resistivity shall be maintained equivalent to Specification
(3)The analytic instruments shall be maintained and cali-
D1193 Type IV. The time averaged value of humidity shall be
brated electronically in accordance with the manufacturers’
within 61% relative humidity of the specified value with
recommendations.Standardgassourcesshallalsobecalibrated
absolute variations no greater than 63% relative humidity
in accordance with the manufacturers’ specifications, or in
from the specified value.
accordance with Practice D3609. Gas concentration analyzers
5.1.2.4 Corrosive Gas Sources—Corrosive(test)gases,such
shall be calibrated to standard gas sources in accordance with
as nitrogen dioxide, hydrogen sulfide, chlorine, sulfur dioxide,
the manufacturers’ recommendations. They shall be calibrated
etc.shallbeofchemicallypure gradeorbetter.Suchgasesare
before and after each test and whenever the indicated concen-
frequently supplied in dry carrier gas such as nitrogen or air.
tration changes exceed the allowed variation in the test
(Warning—This practice involves the use of hazardous
specificatio
...

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.
´2
Designation: B827 − 05 (Reapproved 2009) B827 − 05 (Reapproved 2014)
Standard Practice for
Conducting Mixed Flowing Gas (MFG) Environmental Tests
This standard is issued under the fixed designation B827; 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—Note 3 and the notes in Table 1 were removed editorially in October 2009.
ε NOTE—Footnote 6 was added editorially in May 2010.
1. Scope
1.1 This practice provides procedures for conducting environmental tests involving exposures to controlled quantities of
corrosive gas mixtures.
1.2 This practice provides for the required equipment and methods for gas, temperature, and humidity control which enable tests
to be conducted in a reproducible manner. Reproducibility is measured through the use of control coupons whose corrosion films
are evaluated by mass gain, coulometry, or by various electron and X-ray beam analysis techniques. Reproducibility can also be
measured by in situ corrosion rate monitors using electrical resistance or mass/frequency change methods.
1.3 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
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 become familiar with all hazards including those identified in the appropriate Material Safety Data
Sheet (MSDS) for this product/material as provided by the manufacturer, to establish appropriate safety and health practices, and
determine the applicability of regulatory limitations prior to use. See 5.1.2.4.
2. Referenced Documents
2.1 ASTM Standards:
B542 Terminology Relating to Electrical Contacts and Their Use
B765 Guide for Selection of Porosity and Gross Defect Tests for Electrodeposits and Related Metallic Coatings
B808 Test Method for Monitoring of Atmospheric Corrosion Chambers by Quartz Crystal Microbalances
B810 Test Method for Calibration of Atmospheric Corrosion Test Chambers by Change in Mass of Copper Coupons
B825 Test Method for Coulometric Reduction of Surface Films on Metallic Test Samples
B826 Test Method for Monitoring Atmospheric Corrosion Tests by Electrical Resistance Probes
B845 Guide for Mixed Flowing Gas (MFG) Tests for Electrical Contacts
D1193 Specification for Reagent Water
D2912 Test Method for Oxidant Content of the Atmosphere (Neutral Ki) (Withdrawn 1990)
D2914 Test Methods for Sulfur Dioxide Content of the Atmosphere (West-Gaeke Method)
D3449 Test Method for Sulfur Dioxide in Workplace Atmospheres (Barium Perchlorate Method) (Withdrawn 1989)
D3464 Test Method for Average Velocity in a Duct Using a Thermal Anemometer
D3609 Practice for Calibration Techniques Using Permeation Tubes
D3824 Test Methods for Continuous Measurement of Oxides of Nitrogen in the Ambient or Workplace Atmosphere by the
Chemiluminescent Method
D4230 Test Method of Measuring Humidity with Cooled-Surface Condensation (Dew-Point) Hygrometer
E902 Practice for Checking the Operating Characteristics of X-Ray Photoelectron Spectrometers (Withdrawn 2011)
G91 Practice for Monitoring Atmospheric SO Deposition Rate for Atmospheric Corrosivity Evaluation
This practice is under the jurisdiction of ASTM Committee B02 on Nonferrous Metals and Alloys and is the direct responsibility of Subcommittee B02.11 on Electrical
Contact Test Methods.
Current edition approved Oct. 1, 2009Oct. 1, 2014. Published October 2009October 2014. Originally approved in 1992. Last previous edition approved in 20052009 as
ε2
B827 - 05.B827 – 05 (2009) . DOI: 10.1520/B0827-05R09E02.10.1520/B0827-05R14.
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’sstandard’s Document Summary page on the ASTM website.
The last approved version of this historical standard is referenced on www.astm.org.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
B827 − 05 (2014)
3. Terminology
3.1 Definitions relating to electrical contacts are in accordance with Terminology B542.
4. Significance and Use
4.1 Mixed flowing gas (MFG) tests are used to simulate or amplify exposure to environmental conditions which electrical
contacts or connectors can be expected to experience in various application environments (1, 2).
4.2 Test samples which have been exposed to MFG tests have ranged from bare metal surfaces, to electrical connectors, and
to complete assemblies.
4.3 The specific test conditions are usually chosen so as to simulate, in the test laboratory, the effects of certain representative
field environments or environmental severity levels on standard metallic surfaces, such as copper and silver coupons or porous gold
platings (1, 2).
4.4 Because MFG tests are simulations, both the test conditions and the degradation reactions (chemical reaction rate,
composition of reaction products, etc.) may not always resemble those found in the service environment of the product being tested
in the MFG test. A guide to the selection of simulation conditions suitable for a variety of environments is found in Guide B845.
4.5 The MFG exposures are generally used in conjunction with procedures which evaluate contact or connector electrical
performance such as measurement of electrical contact resistance before and after MFG exposure.
4.6 The MFG tests are useful for connector systems whose contact surfaces are plated or clad with gold or other precious metal
finishes. For such surfaces, environmentally produced failures are often due to high resistance or intermittences caused by the
formation of insulating contamination in the contact region. This contamination, in the form of films and hard particles, is generally
the result of pore corrosion and corrosion product migration or tarnish creepage from pores in the precious metal coating and from
unplated base metal boundaries, if present.
4.7 The MFG exposures can be used to evaluate novel electrical contact metallization for susceptibility to degradation due to
environmental exposure to the test corrosive gases.
4.8 The MFG exposures can be used to evaluate the shielding capability of connector housings which may act as a barrier to
the ingress of corrosive gases.
4.9 The MFG exposures can be used to evaluate the susceptibility of other connector materials such as plastic housings to
degradation from the test corrosive gases.
4.10 The MFG tests are not normally used as porosity tests. For a guide to porosity testing, see Guide B765.
4.11 The MFG tests are generally not applicable where the failure mechanism is other than pollutant gas corrosion such as in
tin-coated separable contacts.
5. Apparatus
5.1 Apparatus required to conduct MFG tests are divided into four major categories, corrosion test chamber, gas supply system,
chamber monitoring system, and chamber operating system.
5.1.1 Corrosion Test Chamber:
5.1.1.1 The chamber shall consist of an enclosure made of nonreactive, low-absorbing, nonmetallic materials contained within
a cabinet or oven capable of maintaining the temperature to a maximum tolerance of 61°C with a preferred tolerance held to
60.5°C within the usable chamber working space accordance with 7.3, with a means to introduce and exhaust gases from the
chamber.
5.1.1.2 The chamber isolates the reactive gases from the external environment. Chamber materials that are not low-absorbing
can affect test conditions by absorbing or emitting reactive gases, leading to control and reproducibility problems. The chamber
construction shall be such that the leak rate is less than 3 % of the volume exchange rate.
5.1.1.3 The chamber shall have provision for maintaining uniformity of the average gas flow velocity within 620 % of a
specified value or of the chamber average when the chamber is empty. For chambers with a dimension of more than 0.5 m,
measurement points shall be in accordance with Test Method B810. For chambers with all dimensions of less than 0.5 m, a
minimum of five points shall be measured at locations in the plane of sample exposure (perpendicular to the expected flow
direction) that are equidistant from each other and the walls of the chamber. After all five or more data values are recorded, all
measurements shall be repeated a second time. After the two sets of measurements are recorded, a third complete set shall be
recorded. The arithmetic average of the 15 or more measurements shall be the chamber average. See 7.5 and 7.6.8. If a hot wire
anemometer is used for gas velocity measurements, it shall be made in accordance with Test Method D3464, with the exception
that sample sites shall be in accordance with Test Method B810.
The boldface numbers in parentheses refer to the list of references at the end of this standard.
B827 − 05 (2014)
5.1.1.4 A sample access port is desirable. This should be designed such that control coupons can be removed or replaced
without interrupting the flow of gases. Corrosion test chamber corrosion rates have been shown to be a function of the presence
or absence of light (3, 4). Provision for controlling the test illumination level in accordance with a test specification shall be made.
5.1.1.5 Examples of test chamber systems are diagrammed in Figs. 1-3. They are not to be considered exclusive examples.
5.1.2 Gas Supply System:
5.1.2.1 Description and Requirements—The gas supply system consists of five main parts: a source of clean, dry, filtered air;
a humidity source; corrosive gas source(s); gas delivery system; and corrosive gas concentration monitoring system(s). Total
supply capacity must be such as to meet requirements for control of gas concentrations. The minimum number of volume changes
is determined by the requirement that the concentration of corrosive gases be maintained within 615 % between gas inlet and
outlet. This is verified by measurement of the gas concentrations near the gas inlet upstream of the usable chamber working volume
and comparing with gas concentrations measured downstream of the usable chamber working volume just prior to the chamber
exhaust; these values shall be within 615 % (see 7.6). Alternative methods of demonstrating compliance with the maximum
allowable concentration gradient are acceptable. Normally, a conditioned chamber equilibrates within several hours after sample
loading and start of the corrosive gas supply. Times longer than 2 h shall be reported in the test report; see Section 8. A guide to
estimating supply requirements is provided in Appendix X1.
NOTE 1—Guidance: when inlet to outlet concentrations vary by more than 615 %, it usually indicates an overloaded chamber.
5.1.2.2 Clean, Dry, Filtered Air Source—Gases other than oxygen and nitrogen that are present in the dry air source shall be
less than or equal to those defined by OHSA Class D limits with the following additional constraint. Gases other than nitrogen,
oxygen, carbon dioxide, noble gases, methane, nitrous oxide, and hydrogen shall be less than 0.005 (ppm) by volume total and
shall be High Efficiency Particulate Arrestants (HEPA) filtered.
5.1.2.3 Humidity Source—The humidity source shall use distilled or deionized water, Specification D1193, Type 1 or better, and
shall introduce no extraneous material. The humidity source shall be maintained equivalent to Specification D1193 Type II or
better, with the exception that electrical resistivity shall be maintained equivalent to Specification D1193 Type IV. The time
averaged value of humidity shall be within 61 % relative humidity of the specified value with absolute variations no greater than
63 % relative humidity from the specified value.
FIG. 1 Schematic Flow-Through Mixed Flowing Gas (MFG) Test System
B827 − 05 (2014)
FIG. 2 Schematic Vertical Recirculating Mixed Flowing Gas (MFG) Test System
FIG. 3 Schematic Horizontal Recirculating Mixed Flowing Gas (MFG) Test System
5.1.2.4 Corrosive Gas Sources—Corrosive (test) gases, such as nitrogen dioxide, hydrogen sulfide, chlorine, sulfur dioxide, etc.
shall be of chemically pure grade or better. Such gases are frequently supplied in dry carrier gas such as nitrogen or air.
(Warning—This practice involves the use of hazardous materials, procedures, and equipment. The gas concentrations in the test
chamber may be within permissible exposure limits (PEL). However, concentrations in the compressed gas cylinders or permeation
devices are often above the PEL, and may exceed the immediately dangerous to life and health level (IDHL). This practice does
not address safety issues associated with MFG testing.)
Chemically Pure and Pre-Purified are designations of Matheson Gas Co., East Rutherford, NJ, for specific grades of purity of gas. Other vendors such as AIRCO have
equivalent gas purities available sold under different terminology.
B827 − 05 (2014)
5.1.2.5 Gas Delivery System—The gas delivery system is comprised of three main parts: gas supply lines, gas control valves
and flow controllers, and a mixing chamber. The gas delivery system shall be capable of delivering gases at the required
concentrations and rates within the test chamber.
(1) All materials used for the gas transport system must not interact with the gases to the extent that chamber gas concentrations
are affected.
(2) Gases, make-up air, and water vapor must be thoroughly mixed before gas delivery to the samples under test in the
chambers. Care must be taken to ensure absence of aerosol formation in the mixing chamber whereby gases are consumed in the
formation of particulates which may interfere with gas concentration control and may introduce corrosion processes which are not
representative of gaseous corrosion mechanisms. Aerosol formation may be detected by the presence of a visible film or deposit
on the interior surface of the gas system where the gases are mixed.
(3) Any fogging of the tubing walls or mixing chamber walls can be taken to be an indication of a loss of corrosive gases from
...