Chemical corrosive gas testing evaluates the resistance of electronic components, connectors, and protective coatings to polluted industrial atmospheres containing trace gases such as hydrogen sulfide, sulfur dioxide, nitrogen dioxide, and chlorine. Performed in accordance with internationally recognized standards including IEC 60068-2-60, ASTM B827, and the ISO 16750 series, this testing helps manufacturers predict product reliability and service life in harsh chemical environments. Accredited third-party laboratories provide mixed flowing gas (MFG) exposure testing, corrosion product analysis, and electrical performance verification for a wide range of industries.
Technical Overview
Chemical corrosive gas testing, also referred to as gas corrosion testing or mixed flowing gas (MFG) testing, is an accelerated environmental test that simulates the long-term effects of contaminated industrial atmospheres on materials, finishes, and electronic assemblies. During exposure, controlled concentrations of corrosive gases such as hydrogen sulfide (H2S), sulfur dioxide (SO2), nitrogen dioxide (NO2), and chlorine (Cl2) react with metal surfaces under specified temperature and humidity conditions. The resulting chemical reactions form sulfides, oxides, and chlorides that degrade surface appearance, solderability, and electrical contact performance.
This type of testing is particularly critical for silver, copper, tin, nickel, and their alloys, which are widely used in electrical contacts, connector platings, and printed circuit board surface finishes. In real-world environments such as petrochemical plants, wastewater treatment facilities, pulp and paper mills, heavily industrialized urban areas, and data centers with elevated levels of airborne sulfur compounds, even parts-per-billion concentrations of corrosive gases can cause creep corrosion, increased contact resistance, and intermittent or complete electrical failure. Standardized laboratory methods compress years of field exposure into test durations of days or weeks, enabling manufacturers to qualify materials, compare protective coating systems, and validate product designs before market release.
Testing Samples
Electrical Contacts and Connectors
Connector housings, contact springs, terminals, relay contacts, and switch components with plated finishes such as gold over nickel, silver, tin, or palladium alloys are among the most frequently tested items, since contact integrity is directly threatened by corrosive gas attack.
Printed Circuit Boards and Assemblies
Bare PCBs with HASL, ENIG, immersion silver, or OSP finishes, as well as fully populated PCB assemblies, are tested to evaluate the corrosion susceptibility of traces, via structures, solder joints, and exposed copper under realistic atmospheric contaminants.
Semiconductor Devices and IC Packages
Integrated circuits, discrete semiconductors, leadframes, and bond wires are evaluated to assess package hermeticity, lead finish durability, and the risk of silver migration or bond pad corrosion in polluted environments.
Metal Platings, Coatings, and Raw Materials
Metal sheet, wire, plated test coupons, and conformal coating samples are exposed to rank material grades, verify plating thickness and porosity, and qualify barrier layers prior to production release.
Finished Electronic Products
Complete modules such as sensors, control units, power supplies, communication equipment, and charging devices may be tested in their final configuration to confirm overall product resistance to chemically aggressive service environments.
Testing Items
Depending on the applicable specification and product requirements, the following evaluations are typically performed before, during, and after gas exposure:
- Visual inspection and discoloration or corrosion grading of exposed surfaces
- Contact resistance measurement before and after exposure
- Insulation resistance and dielectric withstand verification
- Mass change (weight gain) determination of test coupons
- Corrosion product identification and film thickness analysis
- Surface morphology and elemental composition analysis by SEM/EDS
- Cross-sectional metallographic examination of plating layers
- Connector insertion and withdrawal force testing
- Porosity evaluation of noble metal coatings and assessment of creep corrosion behavior
- Functional and electrical performance verification of complete assemblies
Testing Methods
Mixed Flowing Gas Testing to IEC 60068-2-60
Test Ke of IEC 60068-2-60 (equivalently EN 60068-2-60, GB/T 2423.51, and JIS C 60068-2-60) defines four test methods in which samples are exposed to flowing gas mixtures at parts-per-billion concentration levels. Method 1 uses hydrogen sulfide combined with sulfur dioxide, Method 2 combines hydrogen sulfide, nitrogen dioxide, and chlorine, while Methods 3 and 4 apply additional gas combinations and severity levels. Typical test conditions are 25°C to 30°C, 70% to 75% relative humidity, and exposure durations of 4, 7, 10, 14, or 21 days, with copper monitor coupons used to verify chamber corrosivity throughout the test.
Single-Gas Exposure Tests
For evaluating contacts and connections against specific contaminants, IEC 60068-2-42 (Test Kc, sulfur dioxide) and IEC 60068-2-43 (Test Kd, hydrogen sulfide), together with their GB/T 2423.19 and GB/T 2423.20 counterparts, expose samples to elevated ppm-level concentrations of a single gas under controlled temperature and humidity for multi-day durations.
Industry-Specific Procedures
ASTM B827 and ASTM B845 provide standardized practices for conducting and interpreting mixed flowing gas tests for electrical contacts and connectors. The ISO 16750 series defines corrosive gas requirements for electrical and electronic equipment installed in road vehicles, supporting automotive qualification programs. These procedures are often combined with preconditioning and subsequent electrical testing to replicate the full service stress profile.
Post-Test Evaluation
Following exposure, samples are examined visually and microscopically, corrosion films are characterized analytically, and electrical parameters are remeasured and compared against pre-exposure baselines. Results are typically assessed against acceptance criteria defined in the product specification, such as maximum allowable contact resistance change or the absence of visible corrosion products beyond a defined severity level.
Applications
Chemical corrosive gas testing supports reliability qualification and material selection across many sectors where equipment must survive atmospheres contaminated with industrial pollutants:
- Telecommunications infrastructure, including base station hardware and network equipment installed in polluted outdoor environments
- Automotive electronics, control units, and onboard charging components qualified to ISO 16750 requirements
- Aerospace and defense equipment intended for operation in chemically aggressive atmospheres
- Industrial control systems, PLCs, and instrumentation deployed in petrochemical, metallurgical, and power generation plants
- Data centers and server hardware requiring protection against sulfur-induced creep corrosion of silver-finished boards
- New energy equipment such as photovoltaic inverters, energy storage systems, and EV charging stations
- Consumer electronics and connectors intended for global markets with varying ambient air quality
FAQ
What is chemical corrosive gas testing?
It is an accelerated reliability test in which samples are exposed to controlled low concentrations of corrosive gases such as H2S, SO2, NO2, and Cl2 at elevated humidity, in order to reproduce and evaluate the corrosion damage that would occur over years of service in a polluted atmosphere.
How does mixed flowing gas testing differ from salt spray testing?
Mixed flowing gas testing simulates chemically polluted air using trace-level industrial gases and targets mechanisms such as sulfide formation on contacts and finishes, whereas salt spray testing simulates marine or deicing salt environments. The two methods address different corrosion mechanisms and are often both required for comprehensive environmental qualification.
How long does a corrosive gas test take?
Typical exposure durations range from 4 to 21 days depending on the selected method, severity level, and product specification, with additional time required for pre-test conditioning, electrical baseline measurements, and post-test analysis.
Which standards govern this testing?
The most commonly applied standards include IEC 60068-2-60, IEC 60068-2-42, IEC 60068-2-43, ASTM B827, ASTM B845, the ISO 16750 series, and the corresponding GB/T 2423 and JIS C 60068 national adoptions.
What criteria determine whether a sample passes?
Acceptance criteria are defined by the customer specification or applicable product standard and typically include limits on contact resistance change, visual corrosion severity, mass gain of monitor coupons, and preservation of required electrical functionality after exposure.
Can finished products be tested rather than only material coupons?
Yes. Accredited third-party laboratories routinely test complete assemblies in operating or non-operating conditions, which allows the interaction of enclosures, coatings, airflow, and component layout to be evaluated realistically.