Metal strip conductivity testing service

Metal Strip Conductivity Testing Service – Accredited ISO/IEC 17025 Electrical Performance and Material Quality Assessment for the Croatian Market

The electrical conductivity of metal strips is a fundamental material property that directly influences the performance, efficiency, and reliability of components used in electrical power transmission, electronics, automotive wiring, aerospace systems, telecommunications, and renewable energy applications. Conductivity measurements provide critical information about material purity, alloy composition, heat treatment condition, and the presence of defects or contaminants that could compromise electrical performance. In the Croatian market, where the Hrvatski zavod za norme (HZN), the Ministarstvo gospodarstva i održivog razvoja, the Državni inspektorat, the Hrvatska regulatorna agencija za mrežne djelatnosti (HAKOM), and the Carinska uprava enforce strict quality, safety, and energy efficiency standards aligned with EU directives and HRN EN (Croatian standards based on European norms), the accurate evaluation of metal strip conductivity is essential for product certification, material verification, supplier qualification, quality control in manufacturing, and import-export processes. Our laboratory offers a comprehensive metal strip conductivity testing service, applying standardized methods such as the eddy current method (ASTM E1004), the four‑point probe method (ASTM B193), and the bridge method (IEC 60468), to determine the electrical conductivity (in % IACS or MS/m) of a wide range of metal strips, including copper, aluminum, bronze, brass, nickel, silver, and their alloys. 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.

Metal Strip Samples We Regularly Test

Our laboratory receives a wide variety of metal strips and thin metallic components for electrical conductivity testing. Typical samples include:

• Copper and copper alloy strips – for electrical busbars, connectors, transformers, and flexible circuits.
• Aluminum and aluminum alloy strips – for power transmission lines, automotive wiring, and heat sinks.
• Brass and bronze strips – for electrical contacts, connectors, and corrosion-resistant applications.
• Nickel and nickel alloy strips – for battery tabs, heating elements, and high‑temperature applications.
• Silver and silver‑plated strips – for high‑frequency and high‑reliability electrical contacts.
• Gold and gold‑plated strips – for precision electronics and aerospace connectors.
• Prototype and new alloy compositions – submitted by manufacturers for validation of conductivity before series production.
• Field‑retrieved strips and components – for failure analysis and remaining life assessment.

Electrical Conductivity Measurement – Standard Methods and Techniques

We apply a range of standardized test methods to measure the electrical conductivity of metal strips, depending on the material, the thickness, the required accuracy, and the specific application. The choice of the method ensures that the test is appropriate for the sample geometry and that the results are comparable with the specified reference values.

• Eddy current conductivity measurement (ASTM E1004 / ISO 2360 / HRN EN ISO 2360 – for non‑destructive testing) – we use a calibrated eddy current conductivity meter (e.g., a Sigma‑test or a similar instrument) with a suitable probe (diameter 8 mm to 15 mm) to measure the electrical conductivity of the metal strip. The measurement is performed at multiple points across the strip surface (edges, center, and corners) to assess the uniformity. The conductivity is displayed directly in % IACS (International Annealed Copper Standard) or in MS/m (MegaSiemens per meter). We report the average conductivity (in % IACS or MS/m), the minimum and maximum values, the standard deviation, and the uniformity index.
• Four‑point probe conductivity measurement (ASTM B193 / IEC 60468 / HRN EN 60468 – for precise measurement on flat strips) – we use a four‑point probe (or a Kelvin bridge) to measure the resistance of a strip of known dimensions (length, width, and thickness). The probe is placed on the strip surface, and a known current is passed through the two outer probes; the voltage drop between the two inner probes is measured. The sheet resistance (in Ω/square) and the volume resistivity (in μΩ·cm) are calculated. The conductivity (in % IACS) is determined by comparing the measured resistivity with the standard resistivity of annealed copper (1.7241 μΩ·cm at 20 °C). We report the sheet resistance, the volume resistivity, and the conductivity.
• Bridge method for conductivity measurement (ASTM B193 – for high‑accuracy measurements on small samples) – for small or thin strips, we use a precision Wheatstone bridge or a Kelvin double bridge to measure the resistance of a strip of known dimensions. The measurement is performed with a controlled current (to minimize heating) and at a controlled temperature (20 °C ± 1 °C). The resistance is converted to resistivity and conductivity. We report the resistance (in Ω), the resistivity (in μΩ·cm), and the conductivity (in % IACS).
• Temperature correction and conductivity conversion (NTC 5600 – for ensuring comparability) – all conductivity measurements are corrected to the standard reference temperature of 20 °C using the temperature coefficient of the material (e.g., 0.00393 /°C for copper, 0.00403 /°C for aluminum). The measured conductivity (in % IACS) is converted to the SI unit MS/m using the conversion factor: 1 % IACS = 0.58 MS/m. We report the temperature‑corrected conductivity and the conversion result.
• Conductivity measurement on curved or irregular strips (NTC 5601 – for adapted probe techniques) – for strips with a curved surface or a complex geometry, we use a special probe (e.g., a flexible eddy current probe) or we perform the measurement on a flattened section. We report the measurement method and the corrected conductivity.

Test Preparation and Sample Conditioning – Ensuring Accurate and Representative Results

The accuracy of the conductivity measurement depends on the proper preparation of the test sample, including the cleaning of the surface, the measurement of the dimensions, and the control of the temperature. Our procedures strictly follow the requirements of the relevant standards and the best practices of the Croatian and European testing community.

• Surface cleaning and preparation (NTC 5610 – for removing surface contaminants) – we clean the surface of the metal strip using a mild solvent (e.g., isopropyl alcohol) and a lint‑free cloth to remove any oil, grease, oxide, or other contaminants that could affect the measurement. The surface is dried thoroughly before the test. We report the cleaning method and the surface condition.
• Dimensional measurement (NTC 5611 – for the calculation of the resistivity) – we measure the length, the width, and the thickness of the strip (for the four‑point probe and the bridge methods) using a calibrated micrometer or a caliper, with an accuracy of ±0.01 mm. The cross‑sectional area is calculated from the dimensions. We report the measured dimensions and the calculated area.
• Temperature control and measurement (NTC 5612 – for the temperature correction) – we perform the conductivity measurement in a temperature‑controlled room (20 °C ± 1 °C), and we measure the temperature of the strip using a calibrated thermocouple or an infrared thermometer. The temperature is recorded before, during, and after the measurement. We report the temperature and the correction factor.
• Edge and surface condition assessment (NTC 5613 – for the detection of edge defects) – we inspect the edges of the strip for burrs, cracks, or other defects that could affect the conductivity measurement. We report the edge condition and any necessary corrections.
• Sampling and specimen preparation (NTC 5614 – for obtaining representative samples) – we take samples from the strip at the specified locations (e.g., at the beginning, middle, and end of the coil) to ensure that the test results are representative of the entire batch. We report the sampling locations and the number of specimens tested.

Conductivity Uniformity and Mapping – Evaluating the Variation Across the Strip

In many applications, the uniformity of the conductivity across the strip is as important as the average value. Our conductivity mapping tests detect variations in the material properties (e.g., due to inhomogeneous alloying, heat treatment, or thickness variations) and provide a comprehensive assessment of the strip quality.

• Conductivity profiling across the width (NTC 5620 – for evaluating the cross‑directional uniformity) – we measure the conductivity at multiple points across the width of the strip (e.g., at the center, at the edges, and at intermediate positions) to detect any variation in the material properties across the strip. We report the conductivity profile and the maximum variation.
• Longitudinal conductivity scanning (NTC 5621 – for evaluating the uniformity along the strip) – we measure the conductivity at multiple points along the length of the strip (e.g., every 1 meter) to detect any variation due to the processing or the heat treatment. We report the conductivity profile and the statistical parameters.
• Conductivity mapping for large‑area strips (NTC 5622 – for the quality control of large batches) – for large batches of strips, we generate a conductivity map (a 2‑D color contour plot) using a motorized scanning stage and an automated data acquisition system. The map reveals any inhomogeneities, hot spots, or areas of poor conductivity. We report the conductivity map and the statistical parameters.
• Effect of surface defects on conductivity (NTC 5623 – for the detection of local anomalies) – we correlate the conductivity measurements with the surface inspection data (e.g., from visual inspection or optical profilometry) to identify any local defects (e.g., scratches, pits, or contamination) that may affect the conductivity. We report the correlation and the effect of the defects.
• Conductivity after bending or deformation (NTC 5624 – for evaluating the effect of forming) – we measure the conductivity before and after a bending or a forming operation (e.g., a 90° bend) to evaluate the effect of the deformation on the electrical properties. We report the conductivity change and the effect of the deformation.

Influence of Temperature and Heat Treatment – Evaluating the Conductivity after Thermal Exposure

The electrical conductivity of metal strips can be affected by heat treatment, thermal aging, and exposure to elevated temperatures. Our thermal exposure and aging tests simulate the conditions that the strip may encounter during service, and they evaluate the stability of the conductivity and the potential for degradation.

• Thermal aging test (ASTM D573 / ISO 188 / NTC 5630 – for the effect of heat on conductivity) – we age the metal strip in an oven at a specified temperature (e.g., 100 °C, 150 °C, 200 °C) for a specified duration (e.g., 100, 500, or 1000 hours). The conductivity is measured before and after the aging. We report the change in conductivity (in %) and the rate of degradation.
• Annealing and heat treatment evaluation (NTC 5631 – for the effect of the heat treatment on conductivity) – we measure the conductivity of the strip before and after a specified annealing or heat treatment cycle (e.g., 300 °C for 1 hour). The change in conductivity is correlated with the change in the grain size and the microstructure. We report the conductivity after the heat treatment and the change.
• High‑temperature conductivity measurement (NTC 5632 – for evaluating the conductivity at elevated temperatures) – we measure the conductivity of the strip at elevated temperatures (e.g., 50 °C, 100 °C, 150 °C) using a heated test fixture (or a temperature‑controlled chamber). The temperature coefficient of the conductivity is determined. We report the conductivity at each temperature and the temperature coefficient.
• Conductivity recovery after thermal exposure (NTC 5633 – for the evaluation of the reversible effects) – we measure the conductivity before and after a high‑temperature exposure, and then again after a recovery period at room temperature (or after a stress‑relief heat treatment). The recovery of the conductivity is assessed. We report the recovery percentage.
• Correlation with hardness and grain size (NTC 5634 – for the material characterization) – we measure the hardness (Rockwell or Vickers) and the grain size (by metallography) of the strip before and after the heat treatment, and we correlate these properties with the conductivity. We report the hardness, the grain size, and the correlation.

Compliance with Material Specifications and Standards – Pass/Fail Criteria and Guarantee Verification

The measured conductivity is compared with the specified requirements of the relevant material standards (e.g., EN 13599 for copper, EN 485 for aluminum, or the specific customer specifications) to determine the conformity of the strip. Our tests provide a clear pass/fail result and a statement of compliance with the applicable standards.

• Conductivity limit verification (NTC 5640 – for ensuring compliance with the specification) – we compare the measured average conductivity (and the minimum individual reading) with the minimum required value specified in the standard or the purchase order (e.g., 101 % IACS for high‑conductivity copper, 61 % IACS for aluminum 1350). We report the measured values, the required limit, and the pass/fail status.
• Guarantee verification (NTC 5641 – for contractual purposes) – we test the strip to verify that the conductivity is within the guaranteed value specified in the contract or the design specification. We report the measured conductivity and the margin (in %) relative to the guarantee.
• Compliance with European and Croatian standards (HRN EN 13599, HRN EN 485, and others) – we verify the compliance of the strip with the relevant HRN EN standards (which are harmonized with the European EN standards). The compliance statement is included in the test report. We report the compliance and the applicable standard.
• Comparison with reference materials and certified reference materials (CRMs) – NTC 5642 – for the quality assurance) – we use certified reference materials (e.g., conductivity standards) to verify the accuracy of the measurement system. We report the measurement of the CRM and the comparison with the certified value.
• Batch‑to‑batch consistency assessment (NTC 5643 – for the supplier qualification) – we perform conductivity measurements on multiple samples from different batches of the same product, to assess the consistency and the reproducibility of the manufacturing process. We report the statistical parameters and the consistency rating.

Complementary Tests – Tensile Properties, Hardness, and Microstructure for Conductivity Correlation

To provide a comprehensive material characterization and to understand the factors influencing the conductivity, we perform complementary tests, including the measurement of the tensile properties, the hardness, and the microstructure. These tests help explain the conductivity behavior and are essential for the quality control and the material selection.

• Tensile testing (ASTM E8 / ISO 6892 / NTC 5650 – for the yield strength and ductility) – we perform a tensile test on the strip material to determine the yield strength (MPa), the ultimate tensile strength (MPa), the elongation (%), and the modulus of elasticity. We report the tensile properties and the correlation with the conductivity.
• Hardness testing (ASTM E18 / NTC 5651 – Rockwell, Brinell, or Vickers) – we measure the hardness of the strip (HRB, HB, or HV) to verify the heat treatment condition and to detect any localized hardening or softening that may affect the conductivity. We report the hardness values and the uniformity.
• Metallographic examination (ASTM E3 / NTC 5652 – for the grain size and the phase distribution) – we examine the microstructure of the strip (the grain size, the phase distribution, the presence of secondary phases, and the inclusion content) using optical microscopy and SEM. The microstructure is correlated with the conductivity. We report the grain size, the phase distribution, and the inclusion rating.
• Chemical composition analysis (ASTM E415 / NTC 5653 – for the alloy composition) – we use X‑ray fluorescence (XRF) or optical emission spectroscopy (OES) to determine the chemical composition of the strip (the percentage of the main alloying elements). The presence of impurities (e.g., Fe, Si, Mn, Cr, Zn) can significantly reduce the conductivity. We report the composition and the compliance with the specified grade.
• Surface roughness and texture analysis (NTC 5654 – for the influence of the surface finish) – we measure the surface roughness (Ra, Rz) of the strip using a profilometer. The surface roughness can affect the contact resistance and the eddy current measurement. We report the roughness parameters and the correlation with the conductivity.

Test Report and Recognition in the Croatian Electrical, Automotive, and Manufacturing Sector

All procedures described are within the scope of our ISO/IEC 17025 accreditation, with equipment calibrated periodically (conductivity meters, four‑point probes, resistance bridges, tensile test machines, etc.) 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 metal strip (manufacturer, alloy grade, thickness, width, heat number, and surface condition).
• Detailed description of the test methods applied (ASTM/ISO/IEC/HRN EN/NTC standards, test conditions, and measurement parameters).
• Numerical results: electrical conductivity (% IACS, MS/m), volume resistivity (μΩ·cm), sheet resistance (Ω/square), tensile strength (MPa), elongation (%), hardness (HRB/HV), grain size (μm), and chemical composition (%).
• Graphical data: conductivity profiles, conductivity maps, and stress‑strain curves.
• Comparative tables against the values specified by the client or against the limits of the relevant standards (HRN EN 13599, HRN EN 485, ASTM B193, and the requirements of the HZN, HAKOM, and Državni inspektorat).
• Statement of compliance with the applicable material standards and the customer specification.
• Photographs and micrographs of the strip surface and the cross‑section.
• Recommendations for material selection, heat treatment optimization, and quality control measures to achieve the required conductivity.
• 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 energy efficiency compliance, by the Državni inspektorat for market surveillance, by the Hrvatska regulatorna agencija za mrežne djelatnosti (HAKOM) for equipment used in the power grid and telecommunications, and by the Carinska uprava (Croatian Customs) for tariff classification and quality verification in the import of metal strips and electrical components. Additionally, we offer consulting services for the selection of high‑conductivity alloys, the optimization of the manufacturing process, and the implementation of quality control programs for electrical conductivity, contributing to the reliability, efficiency, and sustainability of electrical and electronic systems in the diverse and growing Croatian market, from the power generation and distribution networks to the automotive and consumer electronics industries.