Hydrogen permeability testing service

Hydrogen Permeability Testing Service – Accredited ISO/IEC 17025 Gas Barrier and Compatibility Assessment for the Croatian Market

Hydrogen permeability is a critical parameter that determines the ability of materials to resist the passage of hydrogen gas through their structure. This property is essential for ensuring the safety, efficiency, and reliability of components and systems used in hydrogen production, storage, transport, and utilization, including high‑pressure tanks, pipelines, valves, seals, membranes, and fuel cell components. In the Croatian market, where the Hrvatski zavod za norme (HZN), the Ministarstvo gospodarstva i održivog razvoja, the Državni inspektorat, and the Carinska uprava enforce strict quality, safety, and environmental standards aligned with EU directives and HRN EN (Croatian standards based on European norms), the accurate evaluation of hydrogen permeability is essential for product certification, type testing, supplier qualification, quality control in manufacturing, and import‑export processes. Our laboratory offers a comprehensive hydrogen permeability testing service, applying standardized methods such as ASTM D1434, ISO 15105‑1, ASTM F739, and HRN EN ISO 15105‑1 to measure the steady‑state and transient permeation rates of hydrogen through polymer films, elastomeric seals, composite materials, and metallic membranes under controlled temperature and pressure conditions. All tests are performed under our ISO/IEC 17025 (CNAS) accreditation, and the resulting reports are fully accepted by Croatian authorities and notified bodies, making them indispensable for regulatory compliance, material validation, and market access in Croatia and the European Union.

Test Samples and Materials We Regularly Examine

Our laboratory receives a wide variety of materials and components for hydrogen permeability testing. Typical samples include:

• Polymer films and membranes – polyethylene (PE), polyamide (PA), polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyimide (PI), and other barrier films for hydrogen storage and fuel cell applications.
• Elastomeric seals and gaskets – EPDM, FKM (Viton), NBR, silicone, and other elastomers used in hydrogen systems.
• Composite materials and liners – fiber‑reinforced composites and thermoplastic liners for high‑pressure hydrogen tanks.
• Metallic membranes and foils – palladium, palladium‑alloys, and other metallic membranes for hydrogen separation and purification.
• Prototype and new material formulations – submitted by manufacturers for validation of hydrogen barrier performance before series production.
• Field‑retrieved components – for failure analysis and remaining life assessment.

Steady‑State Hydrogen Permeability Testing – Measuring the Gas Transmission Rate

The steady‑state hydrogen permeability test measures the rate at which hydrogen gas permeates through a material under a constant pressure differential and temperature. Our tests follow international standards and the requirements of the Croatian energy, automotive, and industrial sectors.

• Steady‑state permeability test for films and membranes (ASTM D1434 / ISO 15105‑1 / HRN EN ISO 15105‑1 / NTC 5800) – we mount the test specimen in a permeation cell, with high‑purity hydrogen (or a hydrogen‑nitrogen mixture) on the upstream side at a specified pressure (e.g., 0.1 MPa, 1 MPa, or 10 MPa) and a vacuum or inert gas on the downstream side. The pressure rise on the downstream side is measured over time using a calibrated pressure transducer or a manometer. The steady‑state pressure rise rate is determined, and the hydrogen permeability coefficient (P) and the hydrogen transmission rate (HTR) are calculated. We report the permeability coefficient (in cm³·mm/(m²·day·atm)), the HTR (in cm³/(m²·day)), and the test temperature (typically 23 °C, 40 °C, 60 °C, or 80 °C).
• Permeability test at high pressure (NTC 5801 – for high‑pressure hydrogen systems) – for materials used in high‑pressure hydrogen storage and transport (up to 100 MPa), we perform the permeability test using a high‑pressure cell with a hydrogen pressure of up to 100 MPa. The test is performed at the service temperature. We report the permeability coefficient and the pressure dependence of the permeability.
• Permeability test at different temperatures (NTC 5802 – for the thermal effect on permeability) – we perform the permeability test at multiple temperatures (e.g., 23 °C, 40 °C, 60 °C, 80 °C) to evaluate the temperature dependence of the hydrogen permeability. The activation energy for permeation is calculated from the Arrhenius plot. We report the permeability coefficients at each temperature and the activation energy (in kJ/mol).
• Permeability test for elastomeric seals (NTC 5803 – for O‑rings and gaskets) – we mount an O‑ring or a flat gasket specimen in a permeation cell designed for elastomeric materials, and we measure the hydrogen permeability under a specified compression strain (e.g., 15 %). The test is performed at the service temperature and pressure. We report the permeability coefficient and the effect of compression on the permeability.
• Permeability test with different hydrogen concentrations (NTC 5804 – for the concentration dependence) – we perform the permeability test with different hydrogen partial pressures (e.g., 10 %, 50 %, 100 % hydrogen) to evaluate the concentration dependence of the permeability, which is important for mixed‑gas applications. We report the permeability as a function of the hydrogen partial pressure.

Transient Permeability and Diffusion Coefficient Testing – Understanding the Permeation Kinetics

Transient permeability testing provides insights into the diffusion mechanism and the time required for hydrogen to permeate through a material. The diffusion coefficient and the solubility coefficient are derived from the time‑lag method, providing a more complete characterization of the hydrogen barrier performance.

• Time‑lag method (NTC 5810 – for the determination of the diffusion coefficient) – during the steady‑state permeability test, we monitor the pressure rise on the downstream side continuously from the start of the test. The time lag (τ), defined as the time before the pressure rise becomes linear, is determined. The diffusion coefficient (D) is calculated from the time lag using the equation D = L² / (6 · τ), where L is the specimen thickness. We report the diffusion coefficient (in cm²/s), the solubility coefficient (S = P / D, in cm³/(cm³·atm)), and the time lag (in seconds).
• Diffusion coefficient at different temperatures (NTC 5811 – for the thermal effect on diffusion) – we perform the time‑lag method at multiple temperatures and calculate the diffusion coefficient at each temperature. The activation energy of diffusion is determined. We report the diffusion coefficients and the activation energy of diffusion.
• Diffusion coefficient for different hydrogen concentrations (NTC 5812 – for the concentration‑dependent diffusion) – we perform the permeability test at multiple upstream pressures and calculate the concentration‑dependent diffusion coefficient (which may be pressure‑dependent for some materials). We report the diffusion coefficient as a function of the hydrogen concentration.
• Permeation breakthrough time (NTC 5813 – for the safety assessment) – we measure the time required for the hydrogen to first appear on the downstream side of the specimen (the breakthrough time). The breakthrough time is used to assess the safety margin in barrier applications. We report the breakthrough time (in seconds) and the time to reach a specified concentration.
• Simulation and modeling of the permeation process (NTC 5814 – for the life prediction) – we use the measured permeability, diffusion coefficient, and solubility coefficient to model the hydrogen permeation process in a multi‑layer barrier system. The model is used to predict the hydrogen loss or the hydrogen accumulation over time. We report the model parameters and the predicted permeation behavior.

Hydrogen Embrittlement and Compatibility Testing – Evaluating the Effect of Hydrogen on the Material

In addition to the permeation rate, the interaction of hydrogen with the material can cause hydrogen embrittlement, which reduces the mechanical properties and the service life. Our tests evaluate the compatibility of the material with hydrogen, including the effect of hydrogen on the tensile properties, the fracture toughness, and the fatigue life.

• Hydrogen embrittlement test (ASTM F1459 / NTC 5820 – for the mechanical property degradation) – we expose the test specimen to hydrogen at a specified pressure and temperature for a specified duration, and then we perform a tensile test, a bend test, or a fracture toughness test to evaluate the loss of ductility and the reduction in the strength. We report the retention of the mechanical properties (in %) and the embrittlement index.
• Slow strain rate test (SSRT) in hydrogen (NTC 5821 – for the stress corrosion cracking susceptibility) – we perform a tensile test at a slow strain rate (e.g., 10⁻⁶ s⁻¹) in a hydrogen environment, and we compare the results with the test in an inert environment. The reduction in the elongation and the time to failure are used to assess the susceptibility to hydrogen‑induced cracking. We report the ductility loss, the time to failure, and the fracture morphology.
• Hydrogen permeation and embrittlement correlation (NTC 5822 – for the material selection) – we correlate the measured hydrogen permeability and the diffusion coefficient with the embrittlement susceptibility, to establish a material selection criterion for hydrogen service. We report the correlation and the recommended limit.
• Effect of the hydrogen pressure on the embrittlement (NTC 5823 – for the pressure sensitivity) – we perform the embrittlement test at different hydrogen pressures (e.g., 0.1 MPa, 1 MPa, 10 MPa) to evaluate the pressure sensitivity of the embrittlement. We report the embrittlement index as a function of the pressure.
• Surface and fracture analysis (SEM – ASTM E1508 / NTC 5824 – for the failure mode identification) – we use scanning electron microscopy (SEM) to examine the fracture surface of the embrittled specimen to identify the failure mode (e.g., intergranular fracture, transgranular fracture, or micro‑void coalescence). We report the SEM images and the failure mode.

Barrier Integrity and Defect Detection – Identifying Weak Points in the Hydrogen Barrier

In addition to bulk permeability, localized defects (pinholes, cracks, or delaminations) can significantly increase the hydrogen leakage through a component. Our defect detection and integrity tests identify these weak points, providing a comprehensive assessment of the barrier performance.

• High‑pressure hydrogen leak testing (NTC 5830 – for the detection of leaks) – we pressurize the component with hydrogen (or a hydrogen‑helium mixture) at the service pressure, and we scan the surface for leaks using a hydrogen sensor or a helium mass spectrometer (with helium as a tracer gas). We report the leak rate (in mbar·L/s) and the location of any leaks.
• Bubble leak test (ASTM E515 / NTC 5831 – for detecting pinholes) – we pressurize the test item with hydrogen (or helium) and immerse it in water. The formation of bubbles indicates the location of leaks. We report the size and the location of the leaks.
• Helium leak test (ASTM E493 / NTC 5832 – for high‑sensitivity leak detection) – we use a helium mass spectrometer to detect leaks with a sensitivity of up to 10⁻⁶ mbar·L/s. The test is performed by pressurizing the test item with helium (or by using helium as a tracer gas) and scanning the surface. We report the leak rate and the location of the leaks.
• Ultrasonic and thermographic inspection (NTC 5833 – for the non‑destructive evaluation) – we use ultrasonic testing and infrared thermography to detect delaminations, voids, and other internal defects that could affect the hydrogen barrier. We report the location and the size of any defects.
• Microscopic examination of the barrier layer (NTC 5834 – for the defect analysis) – we examine the barrier layer (e.g., the coating or the liner) using optical microscopy and SEM to detect any pinholes, cracks, or discontinuities. We report the defect density and the defect morphology.

Environmental and Aging Effects on Hydrogen Permeability – Evaluating Durability

The hydrogen permeability of materials can change over time due to thermal aging, UV exposure, chemical attack, and mechanical stress. Our environmental and aging tests evaluate the long‑term stability of the barrier performance, ensuring the reliability of the product over its service life in the diverse Croatian climate (coastal, continental, and mountainous).

• Thermal aging and its effect on permeability (ASTM D573 / ISO 188 / NTC 5840 – for the heat‑aged materials) – we age the material in an oven at a specified temperature (e.g., 70 °C, 100 °C) for a specified duration (e.g., 7, 14, or 28 days), and then we re‑measure the hydrogen permeability. We report the change in the permeability (in %) and the effect of the aging.
• UV aging and its effect on permeability (ASTM G154 / NTC 5841 – for the UV‑exposed materials) – we expose the material to UV radiation (UVA‑340) and condensation cycles for a specified duration (e.g., 500 hours), and then we re‑measure the hydrogen permeability. We report the permeability after UV exposure and the change.
• Chemical exposure and its effect on permeability (ASTM D471 / NTC 5842 – for the chemically exposed materials) – we immerse the material in various chemicals (e.g., mineral oil, 10 % HCl, 10 % NaOH, or a solvent) for a specified duration (e.g., 7 days), and then we re‑measure the hydrogen permeability. We report the permeability after the chemical exposure and the compatibility.
• Humidity and moisture effect (NTC 5843 – for the moisture‑absorbed materials) – we condition the material at a high‑humidity environment (e.g., 40 °C, 95 % RH) for a specified duration (e.g., 7 days), and then we re‑measure the hydrogen permeability. We report the permeability after the humidity exposure and the moisture uptake.
• Mechanical stress and cyclic loading effect (NTC 5844 – for the stress‑enhanced permeation) – we apply a tensile or a cyclic mechanical stress to the material during the hydrogen permeability test, to evaluate the effect of the stress on the permeation rate (stress‑enhanced permeation). We report the permeability as a function of the stress level.

Complementary Tests – Material Characterization and Physical Property Evaluation

To fully understand the hydrogen permeability behavior and to correlate it with the material properties, we perform complementary tests, including material characterization and physical property evaluation.

• Thickness measurement (ASTM D1000 / NTC 5850 – for the film thickness) – we measure the thickness of the specimen (in μm) using a micrometer or a non‑contact optical gauge. The thickness is used for the calculation of the permeability coefficient. We report the average thickness and the thickness variation.
• Density and specific gravity (ASTM D792 / NTC 5851 – for the material density) – we measure the density of the material (in g/cm³) using the Archimedes method. The density is used for the calculation of the solubility coefficient. We report the density.
• FTIR spectroscopy (ASTM E168 / NTC 5852 – for the chemical composition and the degradation) – we use FTIR spectroscopy to identify the chemical composition of the material and to detect any degradation (e.g., oxidation, chain scission) caused by the hydrogen exposure or the aging. We report the FTIR spectra and the chemical changes.
• Thermogravimetric analysis (TGA) – ASTM E1131 / NTC 5853 – for the thermal stability) – we use TGA to measure the thermal stability and the decomposition temperature of the material. The thermal stability is correlated with the hydrogen permeability. We report the decomposition temperature and the mass loss.
• Differential scanning calorimetry (DSC) – ASTM D3418 / NTC 5854 – for the thermal transitions) – we use DSC to measure the glass transition temperature (Tg) and the melting temperature (Tm) of the material. The Tg and the Tm are correlated with the permeability. We report the Tg and the Tm.

Test Report and Recognition in the Croatian Energy, Automotive, and Industrial Sector

All procedures described are within the scope of our ISO/IEC 17025 accreditation, with equipment calibrated periodically (permeation cells, pressure transducers, temperature controllers, and analytical instruments) and traceability to international standards (NIST, PTB). Our test reports are issued in English (with a Croatian summary available on request) and include:

• Full identification of the test sample (material, manufacturer, thickness, and conditioning).
• Detailed description of the test methods applied (ASTM/ISO/HRN EN/NTC standards, test gas, pressure, temperature, and duration).
• Numerical results: hydrogen permeability coefficient (P, cm³·mm/(m²·day·atm)), hydrogen transmission rate (HTR, cm³/(m²·day)), diffusion coefficient (D, cm²/s), solubility coefficient (S, cm³/(cm³·atm)), breakthrough time (s), and embrittlement index (%).
• Graphical data: pressure vs. time curves, Arrhenius plots, and permeability vs. pressure curves.
• Comparative tables against the values specified by the client or against the limits of the relevant standards (ASTM D1434, ISO 15105‑1, ASTM F739, HRN EN ISO 15105‑1, and the requirements of the HZN, Ministarstvo gospodarstva, and Državni inspektorat for hydrogen applications).
• Photographs and micrographs (SEM) of the test specimens before and after the test, showing any degradation, cracking, or damage.
• Recommendations for material selection, design improvement, and quality control measures to achieve the required hydrogen barrier performance.
• Expanded uncertainty (k=2) for all key measurements, calculated according to the ISO/IEC 98‑3 Guide.

These reports are fully accepted by the Hrvatski zavod za norme (HZN) for the verification of product conformity, by the Ministarstvo gospodarstva i održivog razvoja for industrial and energy compliance, by the Državni inspektorat for market surveillance, and by the Carinska uprava (Croatian Customs) for tariff classification and quality verification in the import of materials and components for hydrogen systems. Additionally, we offer consulting services for the selection of hydrogen‑compatible materials, the design of leak‑tight barriers, and the implementation of hydrogen safety programs, contributing to the safety, reliability, and efficiency of hydrogen infrastructure and applications in the diverse and growing Croatian market, from the energy sector to the automotive and industrial manufacturing industries.