ASTM B827-05(2009)e2
(Practice)Standard Practice for Conducting Mixed Flowing Gas (MFG) Environmental Tests
Standard Practice for Conducting Mixed Flowing Gas (MFG) Environmental Tests
SIGNIFICANCE AND USE
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).
Test samples which have been exposed to MFG tests have ranged from bare metal surfaces, to electrical connectors, and to complete assemblies.
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).
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.
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.
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.
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.
The MFG exposures can be us...
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.
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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
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Designation: B827 − 05 (Reapproved2009)
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.
´ NOTE—Note 3 and the notes in Table1 were removed editorially in October 2009.
´ NOTE—Footnote 6 was added editorially in May 2010.
1. Scope B808TestMethodforMonitoringofAtmosphericCorrosion
Chambers by Quartz Crystal Microbalances
1.1 This practice provides procedures for conducting envi-
B810TestMethodforCalibrationofAtmosphericCorrosion
ronmental tests involving exposures to controlled quantities of
Test Chambers by Change in Mass of Copper Coupons
corrosive gas mixtures.
B825Test Method for Coulometric Reduction of Surface
1.2 This practice provides for the required equipment and
Films on Metallic Test Samples
methods for gas, temperature, and humidity control which
B826Test Method for Monitoring Atmospheric Corrosion
enable tests to be conducted in a reproducible manner. Repro-
Tests by Electrical Resistance Probes
ducibility is measured through the use of control coupons
B845Guide for Mixed Flowing Gas (MFG) Tests for Elec-
whosecorrosionfilmsareevaluatedbymassgain,coulometry,
trical Contacts
or by various electron and X-ray beam analysis techniques.
D1193Specification for Reagent Water
Reproducibility can also be measured by in situ corrosion rate
D2912Test Method for Oxidant Content of theAtmosphere
monitors using electrical resistance or mass/frequency change
(Neutral Ki) (Withdrawn 1990)
methods.
D2914Test Methods for Sulfur Dioxide Content of the
1.3 The values stated in SI units are to be regarded as Atmosphere (West-Gaeke Method)
D3449Test Method for Sulfur Dioxide in WorkplaceAtmo-
standard. No other units of measurement are included in this
standard. spheres (Barium Perchlorate Method) (Withdrawn 1989)
D3464Test Method forAverage Velocity in a Duct Using a
1.4 This standard does not purport to address all of the
Thermal Anemometer
safety concerns, if any, associated with its use. It is the
D3609Practice for Calibration Techniques Using Perme-
responsibility of the user of this standard to become familiar
ation Tubes
with all hazards including those identified in the appropriate
D3824Test Methods for Continuous Measurement of Ox-
Material Safety Data Sheet (MSDS) for this product/material
idesofNitrogenintheAmbientorWorkplaceAtmosphere
as provided by the manufacturer, to establish appropriate
by the Chemiluminescent Method
safety and health practices, and determine the applicability of
D4230Test Method of Measuring Humidity with Cooled-
regulatory limitations prior to use. See 5.1.2.4.
Surface Condensation (Dew-Point) Hygrometer
2. Referenced Documents E902Practice for Checking the Operating Characteristics of
2 X-Ray Photoelectron Spectrometers (Withdrawn 2011)
2.1 ASTM Standards:
G91Practice for Monitoring Atmospheric SO Deposition
B542Terminology Relating to Electrical Contacts andTheir
Rate for Atmospheric Corrosivity Evaluation
Use
B765GuideforSelectionofPorosityandGrossDefectTests
3. Terminology
for Electrodeposits and Related Metallic Coatings
3.1 Definitions relating to electrical contacts are in accor-
dance with Terminology B542.
ThispracticeisunderthejurisdictionofASTMCommitteeB02onNonferrous
Metals and Alloys and is the direct responsibility of Subcommittee B02.11 on
4. Significance and Use
Electrical Contact Test Methods.
Current edition approved Oct. 1, 2009. Published October 2009. Originally
4.1 Mixed flowing gas (MFG) tests are used to simulate or
approved in 1992. Last previous edition approved in 2005 as B827-05. DOI:
amplify exposure to environmental conditions which electrical
10.1520/B0827-05R09E02.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
Standards volume information, refer to the standard’s Document Summary page on The last approved version of this historical standard is referenced on
the ASTM website. www.astm.org.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
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B827 − 05 (2009)
contactsorconnectorscanbeexpectedtoexperienceinvarious 5.1.1.1 The chamber shall consist of an enclosure made of
application environments (1, 2). nonreactive, low-absorbing, nonmetallic materials contained
within a cabinet or oven capable of maintaining the tempera-
4.2 Test samples which have been exposed to MFG tests
ture to a maximum tolerance of 61°C with a preferred
have ranged from bare metal surfaces, to electrical connectors,
tolerance held to 60.5°C within the usable chamber working
and to complete assemblies.
space accordance with 7.3, with a means to introduce and
4.3 The specific test conditions are usually chosen so as to
exhaust gases from the chamber.
simulate, in the test laboratory, the effects of certain represen-
5.1.1.2 The chamber isolates the reactive gases from the
tative field environments or environmental severity levels on
external environment. Chamber materials that are not low-
standard metallic surfaces, such as copper and silver coupons
absorbing can affect test conditions by absorbing or emitting
or porous gold platings (1, 2).
reactivegases,leadingtocontrolandreproducibilityproblems.
4.4 Because MFG tests are simulations, both the test con-
Thechamberconstructionshallbesuchthattheleakrateisless
ditions and the degradation reactions (chemical reaction rate,
than 3% of the volume exchange rate.
composition of reaction products, etc.) may not always re-
5.1.1.3 The chamber shall have provision for maintaining
semble those found in the service environment of the product
uniformity of the average gas flow velocity within 620%ofa
being tested in the MFG test. A guide to the selection of
specifiedvalueorofthechamberaveragewhenthechamberis
simulation conditions suitable for a variety of environments is
empty. For chambers with a dimension of more than 0.5 m,
found in Guide B845.
measurement points shall be in accordance with Test Method
B810. For chambers with all dimensions of less than 0.5 m, a
4.5 The MFG exposures are generally used in conjunction
minimum of five points shall be measured at locations in the
with procedures which evaluate contact or connector electrical
plane of sample exposure (perpendicular to the expected flow
performance such as measurement of electrical contact resis-
direction) that are equidistant from each other and the walls of
tance before and after MFG exposure.
thechamber.Afterallfiveormoredatavaluesarerecorded,all
4.6 The MFG tests are useful for connector systems whose
measurements shall be repeated a second time. After the two
contact surfaces are plated or clad with gold or other precious
setsofmeasurementsarerecorded,athirdcompletesetshallbe
metal finishes. For such surfaces, environmentally produced
recorded. The arithmetic average of the 15 or more measure-
failures are often due to high resistance or intermittences
ments shall be the chamber average. See7.5 and 7.6.8.Ifahot
caused by the formation of insulating contamination in the
wire anemometer is used for gas velocity measurements, it
contact region. This contamination, in the form of films and
shallbemadeinaccordancewithTestMethodD3464,withthe
hard particles, is generally the result of pore corrosion and
exception that sample sites shall be in accordance with Test
corrosion product migration or tarnish creepage from pores in
Method B810.
the precious metal coating and from unplated base metal
5.1.1.4 A sample access port is desirable. This should be
boundaries, if present.
designedsuchthatcontrolcouponscanberemovedorreplaced
4.7 The MFG exposures can be used to evaluate novel
without interrupting the flow of gases. Corrosion test chamber
electricalcontactmetallizationforsusceptibilitytodegradation
corrosion rates have been shown to be a function of the
due to environmental exposure to the test corrosive gases.
presenceorabsenceoflight (3, 4).Provisionforcontrollingthe
4.8 The MFG exposures can be used to evaluate the test illumination level in accordance with a test specification
shielding capability of connector housings which may act as a shall be made.
barrier to the ingress of corrosive gases.
5.1.1.5 Examples of test chamber systems are diagrammed
inFigs.1-3.Theyarenottobeconsideredexclusiveexamples.
4.9 The MFG exposures can be used to evaluate the
5.1.2 Gas Supply System:
susceptibility of other connector materials such as plastic
housings to degradation from the test corrosive gases.
5.1.2.1 Description and Requirements—Thegassupplysys-
tem consists of five main parts: a source of clean, dry, filtered
4.10 TheMFGtestsarenotnormallyusedasporositytests.
air; a humidity source; corrosive gas source(s); gas delivery
For a guide to porosity testing, see Guide B765.
system; and corrosive gas concentration monitoring system(s).
4.11 The MFG tests are generally not applicable where the
Totalsupplycapacitymustbesuchastomeetrequirementsfor
failuremechanismisotherthanpollutantgascorrosionsuchas
controlofgasconcentrations.Theminimumnumberofvolume
in tin-coated separable contacts.
changes is determined by the requirement that the concentra-
tion of corrosive gases be maintained within 615% between
5. Apparatus
gas inlet and outlet.This is verified by measurement of the gas
5.1 Apparatus required to conduct MFG tests are divided
concentrations near the gas inlet upstream of the usable
into four major categories, corrosion test chamber, gas supply
chamber working volume and comparing with gas concentra-
system, chamber monitoring system, and chamber operating
tions measured downstream of the usable chamber working
system.
volumejustpriortothechamberexhaust;thesevaluesshallbe
5.1.1 Corrosion Test Chamber:
within 615% (see 7.6).Alternative methods of demonstrating
compliance with the maximum allowable concentration gradi-
ent are acceptable. Normally, a conditioned chamber equili-
Theboldfacenumbersinparenthesesrefertothelistofreferencesattheendof
this standard. brateswithinseveralhoursaftersampleloadingandstartofthe
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B827 − 05 (2009)
etc.shallbeofchemicallypure gradeorbetter.Suchgasesare
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 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
FIG. 1 Schematic Flow-Through Mixed Flowing Gas (MFG) Test
the gases are mixed.
System
(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
corrosivegassupply.Timeslongerthan2hshallbereportedin
should occur inside a separate area of, or as close as possible
the test report; see Section 8. A guide to estimating supply
to, the test chamber so as to ensure thermal equilibration with
requirements is provided in Appendix X1.
the test chamber.
NOTE 1—Guidance: when inlet to outlet concentrations vary by more
(4)Flow measurement capability is required at the inlet of
than 615%, it usually indicates an overloaded chamber.
the chamber and also at the exhaust of negative pressure
5.1.2.2 Clean, Dry, Filtered Air Source—Gases other than
chambers to ensure the absence of uncalibrated gas streams.
oxygen and nitrogen that are present in the dry air source shall
5.1.2.6 Corrosive Gas Concentration Monitoring System—
be less than or equal to those defined by OHSAClass D limits
Standard measurement systems for very low level gas concen-
with the following additional constraint. Gases other than
trations are listed in Table 1, which provides for gases in
nitrogen, oxygen, carbon dioxide, noble gases, methane, ni-
common use in present mixed flowing gas systems, for testing
trous oxide, and hydrogen shall be less than 0.005 (ppm) by
electrical contact performance.
volumetotalandshallbeHighEfficiencyParticulateArrestants
(1)Each instrument must be characterized for interference
(HEPA) filtered.
with the gases specified, both individually and mixed.
5.1.2.3 Humidity Source—The humidity source shall use
(2)Depending on the exact equipment set used, it may not
distilled or deionized water, Specification D1193,Type1or
be possible to accurately measure the concentration of some
better, and shall introduce no extraneous material. The humid-
gases, such as chlorine, in combination with any of the other
ity source shall be maintained equivalent to Specification
gases.
D1193 Type II or better, with the exception that electrical
(3)The analytic instruments shall be maintained and cali-
resistivity shall be maintained equivalent to Specification
brated electronically in accordance with the manufacturers’
D1193 Type IV. The time averaged value of humidity shall be
recommendations.Standardgassourcesshallalsobecalibrated
within 61% relative humidity of the specified value with
absolute variations no greater than 63% relative humidity
Chemically Pure and Pre-Purified are designations of Matheson Gas Co., East
from the specified value.
Rutherford, NJ, for specific grades of purity of gas. Other vendors such asAIRCO
5.1.2.4 Corrosive Gas Sources—Corrosive(test)gases,such
have equivalent gas
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