Rubber gas corrosion testing evaluates the resistance of elastomeric materials and finished components to corrosive gases such as sulfur dioxide, hydrogen sulfide, nitrogen dioxide, chlorine, and ozone under controlled temperature and humidity conditions. This testing is essential for verifying the long-term reliability of rubber seals, gaskets, hoses, and insulating parts used in automotive, electronics, petrochemical, and other harsh-environment industries. By simulating aggressive atmospheric conditions in an accelerated laboratory setting, manufacturers can predict service life, compare material formulations, and qualify products against international standards.
Technical Overview
Rubber gas corrosion testing is an accelerated environmental test that exposes rubber materials and components to controlled concentrations of corrosive gases in order to assess their chemical resistance and aging behavior. In industrial atmospheres, rubber products frequently encounter sulfur dioxide (SO₂), hydrogen sulfide (H₂S), nitrogen dioxide (NO₂), chlorine (Cl₂), and ozone (O₃), often combined with elevated temperature and high relative humidity. These gases can attack polymer chains, react with fillers and cure-system residues, and degrade the metal inserts or contacts integrated into rubber assemblies.
Unlike metals, where corrosion manifests as surface oxidation, rubber degradation appears as discoloration, surface cracking, blistering, hardening or softening, loss of elasticity, and reduced tensile performance. Gas corrosion testing therefore combines chemical exposure with mechanical and physical characterization before and after the test. Commonly applied standards include IEC 60068-2-42 (sulfur dioxide test), IEC 60068-2-43 (hydrogen sulfide test), IEC 60068-2-60 (flowing mixed gas corrosion test), ISO 21207, ASTM B845, ASTM D1149, ISO 1431-1, and GB/T 2423.51, which define gas concentrations, temperature, humidity, exposure duration, and evaluation criteria.
Testing Samples
Standard Vulcanized Rubber Specimens
Test laboratories typically receive vulcanized rubber sheets from which dumbbell-shaped specimens are die-cut according to ISO 37 or ASTM D412. These standardized specimens allow accurate measurement of tensile strength and elongation changes after gas exposure. Flat plaque specimens are also used for hardness, mass, and dimensional measurements.
Finished Rubber Components
Complete products such as O-rings, gaskets, diaphragms, rubber seals for electrical enclosures, cable accessories, vibration isolators, and rubber-coated metal parts can be tested in their end-use configuration. Testing finished components reveals design weaknesses, such as thin cross-sections or bonded interfaces, that coupon testing alone cannot detect.
Various Elastomer Families
- Natural rubber (NR) and styrene-butadiene rubber (SBR) for general-purpose applications
- Nitrile butadiene rubber (NBR) for fuel and oil-resistant sealing systems
- Ethylene propylene diene monomer (EPDM) for outdoor and chemical-resistant applications
- Chloroprene rubber (CR) for weather and ozone resistance
- Silicone rubber (VMQ) and fluorosilicone (FVMQ) for wide-temperature-range sealing
- Fluoroelastomers (FKM) for aggressive chemical and high-temperature environments
Testing Items
A comprehensive gas corrosion test program evaluates the following parameters before and after exposure:
- Visual appearance: discoloration, surface tackiness, cracking, blistering, or efflorescence, often rated against photographic reference scales
- Mass change: percentage increase or decrease indicating absorption, extraction, or chemical reaction
- Dimensional change: swelling or shrinkage measured on critical sealing dimensions
- Hardness change: Shore A or IRHD hardness deviation indicating crosslink density changes
- Tensile strength and elongation at break: retention percentages calculated from stress-strain testing
- Compression set: permanent deformation after sustained compression, critical for sealing performance
- Corrosion of associated metal parts: evaluation of contacts, inserts, or plated surfaces integrated with the rubber component
- Sealing performance: leakage or pressure-decay testing to confirm functional integrity after exposure
Testing Methods
Single-Gas Exposure Tests
Single-gas tests expose specimens to one corrosive gas at a defined concentration. The sulfur dioxide test per IEC 60068-2-42 and the hydrogen sulfide test per IEC 60068-2-43 are widely used for silver-bearing contacts and connections, and they are equally applicable to rubber parts used in gaseous or mildly polluted industrial atmospheres. Typical conditions involve gas concentrations of 10–25 ppm at 25 °C to 40 °C with relative humidity near 75 percent.
Mixed Flowing Gas Tests
Mixed flowing gas (MFG) tests combine two to four corrosive gases to replicate severe industrial environments more realistically. IEC 60068-2-60 defines four test methods with different combinations of H₂S, SO₂, NO₂, and Cl₂, at concentrations ranging from 10 ppb to 200 ppb, temperatures of 25 °C or 30 °C, and 70–75 percent relative humidity. ASTM B845 and GB/T 2423.51 describe equivalent mixed-gas procedures. Exposure durations commonly span 4, 7, 10, 14, or 21 days depending on the severity level agreed between manufacturer and customer.
Ozone Resistance Testing
Because ozone is one of the most aggressive agents for rubber, dedicated ozone tests are often performed alongside corrosive gas testing. ISO 1431-1, ASTM D1149, and GB/T 7762 specify static or dynamic strain exposure at ozone concentrations of 50 pphm or as agreed, typically at 40 °C, with visual crack-rating criteria under magnification.
Test Procedure and Evaluation
A typical test sequence consists of specimen conditioning, initial measurements of appearance, mass, dimensions, hardness, and tensile properties, followed by exposure in a calibrated corrosion chamber with continuous monitoring of gas concentration, temperature, and humidity. After exposure, specimens are rested and re-measured, retention values are calculated, and a test report documents all conditions, deviations, and results in accordance with the selected standard.
Applications
- Automotive industry: fuel system seals, engine bay components, EV battery pack gaskets, and underbody parts exposed to exhaust gases and road environments
- Electronics and electrical equipment: enclosure gaskets, connector seals, and cable accessories exposed to indoor industrial atmospheres containing sulfur compounds
- Petrochemical and refining: pipeline gaskets, valve seats, and expansion joints in contact with sour gas and acidic process streams
- Power generation and transmission: transformer gaskets, insulator components, and substation hardware in polluted atmospheres
- Rail transit and marine engineering: door seals, window gaskets, and hatch seals exposed to high-humidity, salt-laden, or industrial-polluted air
- Aerospace: seals and vibration mounts qualified for chemically aggressive and high-altitude ozone-rich environments
Accredited third-party laboratories provide these tests for material qualification, incoming inspection, failure analysis, and product certification support, helping manufacturers demonstrate compliance with customer specifications and regulatory requirements.
FAQ
Which gases are most commonly used in rubber gas corrosion testing?
The most frequently used gases are sulfur dioxide, hydrogen sulfide, nitrogen dioxide, and chlorine in mixed flowing gas tests, along with ozone for dedicated ozone-cracking resistance tests. Gas selection depends on the target service environment and the applicable standard.
How long does a typical gas corrosion test take?
Standard exposure durations are 4, 7, 10, 14, or 21 days, although extended exposures of up to 28 days or longer may be specified for severe-service qualifications. Additional time is required for pre-test conditioning and post-test mechanical evaluation.
What is the difference between ozone testing and mixed gas corrosion testing?
Ozone testing per ISO 1431-1 or ASTM D1149 focuses on surface cracking of rubber under tensile strain, whereas mixed gas corrosion testing per IEC 60068-2-60 or GB/T 2423.51 evaluates chemical degradation and corrosion caused by combinations of industrial pollutant gases, including effects on attached metals and finishes.
How are test results interpreted?
Results are typically expressed as percentage retention of tensile strength and elongation, change in hardness and mass, visual crack ratings, and pass/fail corrosion classification of associated metal parts. Acceptance criteria are defined by product specifications, industry standards, or customer requirements.