Mixed Flow gas (MFG) testing is critical for quality control and assessing the corrosion potential of electrical components that will be exposed to atmospheric and potentially sealed conditions. Our organization provides MFG testing services to the aerospace, automotive, consumer goods and medical device industries.
What is MFG test
The purpose of the MFG test is to simulate real corrosion from environmental exposure conditions. Our organization allows you to evaluate the performance of your products by creating controlled test conditions where temperature (°C), relative humidity (%RH) and gaseous pollutant concentrations, as well as other key variables, are carefully defined, monitored and controlled.
Common gases used for testing include:
Chlorine
Hydrogen sulfide
Nitrogen dioxide
Sulfur dioxide
Common test standards:ASTM B827 and ASTM B845
ASTM B827
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 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 mainly 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.
ASTM B845
Significance and Use
4.1 Preservation of a conducting surface on electrical contact is vital to the continued functioning of such contacts. Contamination of the surface with insulating layers formed by corrosion processes is one potential hazard. Laboratory testing of contacts in MFG tests is used to assess the effectiveness of design features and materials.
4.2 MFG tests are used in development studies of processes and materials for contacts. For example, coupon specimens may be exposed to MFG tests to evaluate new contact materials, layers of new coating materials on a supporting substrate, reduced coating thicknesses, or protective surface treatments.
4.3 MFG tests are also employed to test the durability of a finished product with respect to atmospheric corrosion. For example, finished connectors may be exposed to a MFG test and their performances compared against each other or against a set of fixed requirements. Relays or switch contacts may be exposed in the operated and non-operated conditions to compare performance.
4.4 MFG tests are useful for determining the effectiveness of connector housings and shrouds as barriers to ingress of atmospheric corrodants to the contact surfaces. These tests can also be used to assess the screening of the metal-to-metal contact areas of mated connectors.
4.5 MFG tests are employed as qualification tests to determine connector failure rates in application environments for which correlation between test and application has previously been established.
4.6 This guide provides test conditions which are to be applied in conjunction with Practice B827 which defines the required test operation and certification procedures, tolerances, and reporting requirements. Where the test specifier requires certifications or tolerances different than those provided in Practice B827, the required certifications or tolerances shall be part of the test specification. Differences from the specifications in Practice B827 shall be reported in the test report provided by the test operator to the test specifier. Specification of one of the test conditions defined in this document in the form of a statement such as, "Parts shall be tested in accordance with ASTM B845 Method Z," implicitly requires test condition, Z, applied according to Practice B827.
MFG test chamber
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