The Chemically Active Substances Aging Test is an accelerated environmental test that evaluates the resistance of materials, components, and finished products to degradation caused by exposure to corrosive gases such as sulfur dioxide, hydrogen sulfide, nitrogen dioxide, chlorine, and ozone. Performed in accordance with internationally recognized standards including IEC 60068-2, ISO 9227, ISO 10062, and ASTM B845, this test helps manufacturers verify long-term reliability in industrial, urban, and marine service environments. Accredited third-party laboratories provide comprehensive evaluation of corrosion resistance, contact performance, and material integrity after chemically aggressive exposure.
Technical Overview
The Chemically Active Substances Aging Test, also referred to as corrosive gas aging testing or environmental corrosion testing, is a laboratory technique used to simulate and accelerate the degradation mechanisms that occur when products are exposed to chemically aggressive atmospheres. During the test, specimens are placed inside a controlled environmental chamber and subjected to defined concentrations of chemically active substances, including sulfur dioxide (SO2), hydrogen sulfide (H2S), nitrogen dioxide (NO2), chlorine (Cl2), ozone (O3), and salt mist, under precisely regulated temperature and humidity conditions. These conditions reproduce, in an accelerated timeframe, the corrosive environments found in industrial zones, urban areas with heavy traffic, chemical processing plants, coastal marine locations, and indoor electronic equipment rooms.
The primary degradation mechanisms evaluated by this test include electrochemical corrosion of metals, sulfidation and tarnishing of silver and copper contact surfaces, oxidation of base materials, hydrolysis and embrittlement of polymers, delamination of coatings and platings, and ozone-induced cracking of elastomers. Because even parts-per-billion concentrations of pollutant gases can cause contact failure in electronic systems over time, standards such as IEC 60068-2-60 define mixed flowing gas methods with gas concentrations ranging from 10 ppb to 200 ppb at temperatures of 25 °C to 30 °C and relative humidity of 70 % to 75 %. Test durations typically extend from 4 to 21 days, with longer exposures used to simulate service lives of 10 years or more in harsh environments.
- Simulates industrial, urban, marine, and process gas environments in a controlled chamber
- Accelerates corrosion and material aging mechanisms to evaluate long-term reliability
- Supports design verification, material selection, qualification, and quality control
- Provides quantifiable data on contact resistance, appearance, mass change, and functionality
Testing Samples
Electrical Contacts and Connectors
Contacts, connectors, relays, switches, and terminal blocks with silver, copper alloy, tin-plated, nickel-plated, or gold-plated contact surfaces are among the most common test subjects. These components are highly sensitive to trace concentrations of sulfur-bearing gases, which form insulating sulfide films that increase contact resistance and cause signal or power interruption. Tests are typically performed on unassembled contacts, mated connector pairs, or complete switching devices according to IEC 60068-2-43 and IEC 60068-2-60.
Printed Circuit Boards and Electronic Assemblies
Bare boards, printed circuit board assemblies, solder joints, surface finishes such as ENIG, OSP, and HASL, as well as conformally coated and molded assemblies, are tested to assess copper migration, pad corrosion, solder degradation, and coating barrier performance under chemically active atmospheres.
Metallic Materials and Protective Coatings
Steel, zinc alloys, aluminum alloys, stainless steel, anodized parts, electroplated components, painted surfaces, and fastening systems are exposed to evaluate coating integrity, pore density, underfilm corrosion, white rust and red rust formation, and overall corrosion penetration depth.
Polymeric and Elastomeric Materials
Rubber seals, gaskets, O-rings, cable insulation, thermoplastic housings, and adhesive joints are tested for ozone cracking, surface degradation, hardening, loss of elasticity, and retention of tensile strength and elongation after exposure, following methods such as ISO 1431 and ASTM D1149.
Finished Products and Assemblies
Complete products including automotive electronic control units, telecommunications hardware, industrial control equipment, household appliances, lighting products, and energy storage components are tested as delivered, in their final packaging, or in operating configurations to verify real-world chemical environmental resistance.
Testing Items
Evaluation of specimens before, during, and after chemically active substance exposure covers a comprehensive set of measurable parameters. Common testing items include the following:
- Visual inspection: discoloration, tarnishing, corrosion product formation, blistering, cracking, and delamination
- Contact resistance measurement of contacts and connector interfaces before and after exposure
- Insulation resistance and dielectric withstand voltage testing of electronic assemblies
- Mass change determination to quantify corrosion or film growth
- Corrosion morphology analysis, corrosion depth measurement, and pit density evaluation
- Porosity testing of precious metal platings over susceptible underplates
- Coating adhesion, thickness verification, and barrier integrity assessment
- Mechanical property retention testing of polymers, including tensile strength and elongation at break
- Functional and electrical performance verification after exposure conditioning
Testing Methods
Static Sulfur Dioxide Test (Kesternich Type)
Specimens are exposed to a static atmosphere containing a defined quantity of sulfur dioxide, typically 0.2, 1.0, or 2.0 liters of SO2 per 300-liter chamber volume, at 40 °C with near-saturation humidity in cyclic exposures. This method, standardized in ISO 6988, IEC 60068-2-42, and GB/T 2423.19, is widely used for evaluating protective coatings, painted surfaces, metallic components, and corrosion protection systems against acid rain and industrial atmospheres.
Static Hydrogen Sulfide Test
This method exposes specimens, particularly silver and copper alloy contacts, to hydrogen sulfide concentrations of approximately 10 to 15 ppm at 25 °C and 75 % relative humidity for durations of 4, 10, or 21 days. Standardized in IEC 60068-2-43 and GB/T 2423.20, it evaluates the tendency of contact materials to form resistive sulfide tarnish films that degrade electrical performance.
Mixed Flowing Gas (MFG) Test
The mixed flowing gas method is the most representative test for modern electronic equipment environments. Specimens are continuously exposed to a flowing atmosphere containing parts-per-billion levels of multiple pollutant gases, typically combinations of H2S, SO2, NO2, and Cl2, at 25 °C to 30 °C and 70 % to 75 % relative humidity. IEC 60068-2-60 defines four severity methods, complemented by ASTM B827, ASTM B845, ISO 10062, and GB/T 2423.51. Exposure durations of 4, 7, 10, 14, or 21 days correspond to varying service severity levels, and copper reference coupons monitored per ASTM B810 verify the corrosivity of the test atmosphere.
Cyclic Salt Mist and Combined Corrosion Tests
Salt mist tests using sodium chloride solution simulate marine and de-icing salt environments and are performed as continuous spray or cyclic tests combining salt deposition, dry storage, and humid storage phases. Applicable standards include IEC 60068-2-52, ISO 9227, ASTM B117, JIS Z 2371, and GB/T 2423.17 and GB/T 2423.18. Combined cyclic tests that alternate humidity cycling with corrosive gas exposure, such as ISO 21207, provide severe accelerated conditions for automotive and heavy industrial applications.
Ozone Aging Test
Elastomeric materials are exposed to controlled ozone concentrations under static or dynamic strain at specified temperature to assess cracking resistance. ISO 1431 and ASTM D1149 define ozone concentrations ranging from 25 pphm to 200 pphm with exposure durations selected according to the intended service environment.
Applications
Chemically active substances aging testing is applied across industries where atmospheric corrosivity, pollutant exposure, or chemical process environments can compromise product reliability. Typical application areas include:
- Automotive electronics: validation of engine management units, sensors, wiring systems, and connectors against sulfur and salt environments referenced in ISO 16750 series requirements
- Telecommunications and data centers: qualification of servers, switching equipment, and connector systems against data center corrosive gas classes
- Industrial automation: reliability of PLCs, control cabinets, and instrumentation in chemical plants and heavy industry
- Aerospace and rail transit: assessment of avionics and onboard equipment exposed to atmospheric pollutants and cleaning agents
- Energy and power systems: corrosion evaluation of photovoltaic components, battery systems, transformers, and grid infrastructure
- Consumer electronics and appliances: material and coating qualification for humid, polluted, or coastal usage conditions
- Metallurgy and plating industries: benchmarking of surface treatments, passivation processes, and protective coating systems
FAQ
What is the difference between a chemically active substances aging test and a damp heat test?
A damp heat test exposes specimens only to elevated temperature and humidity, evaluating moisture-related degradation, whereas a chemically active substances test adds defined concentrations of corrosive gases or salt mist to the atmosphere. The chemical test therefore evaluates corrosion, sulfidation, and chemically driven aging mechanisms that damp heat testing alone cannot reproduce, and the two methods are often combined in sequential or cyclic qualification programs.
How long does a typical test take?
Durations depend on the selected method and severity level. Static hydrogen sulfide and mixed flowing gas tests commonly run 4, 7, 10, 14, or 21 days, Kesternich sulfur dioxide tests typically run 1 to 8 cycles of 24 hours each, and cyclic salt mist tests may run from 72 hours to several weeks. Accredited third-party laboratories can advise on severity selection based on the intended service environment and product life requirement.
What samples and quantities are required?
Representative samples in their production configuration, including the actual materials, platings, coatings, and protective treatments, should be submitted. For statistical validity, a minimum of three specimens per condition is generally recommended, plus reference specimens retained for comparison. Where mixed flowing gas testing is performed, sufficient chamber space must be available to maintain uniform gas flow around each specimen.
How are test results judged?
Acceptance criteria are defined by product specifications or applicable standards and commonly include limits on contact resistance increase, absence of corrosive products affecting function, allowable appearance changes, mass change limits, and retention of electrical and mechanical performance. Detailed photographic documentation, measured data, and a structured test report are provided so that design and quality teams can perform engineering assessment.
Is the test destructive?
Yes, exposure to chemically active substances generally alters surface condition and may permanently affect appearance and performance, so tested specimens should not be returned to service or resale. For this reason, dedicated test samples rather than production units are normally submitted, with any required functional assessment performed at the laboratory immediately after exposure.