Surface Roughness Inspection Service

Surface Roughness Inspection Service – Accredited ISO/IEC 17025 Surface Texture and Quality Assessment for the Croatian Market

Surface roughness is a critical quality parameter that quantifies the microscopic texture of a surface, characterized by its peaks, valleys, and irregularities. This property directly influences the performance, durability, and functionality of components in industries such as automotive, aerospace, medical devices, precision engineering, electronics, and construction. 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 and performance standards aligned with EU directives and HRN EN (Croatian standards based on European norms), the accurate evaluation of surface roughness is essential for product certification, supplier qualification, quality control in manufacturing, and import‑export processes. Our laboratory offers a comprehensive surface roughness inspection service, applying standardized methods such as ISO 4287, ISO 4288, ISO 13565, ASME B46.1, and HRN EN ISO 4287 to measure surface roughness parameters (Ra, Rz, Rq, Rmax, Rsk, Rku, RSm, and RΔq) using contact and non‑contact profilometry techniques. 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, product validation, and market access in Croatia and the European Union.

Surface Samples and Components We Regularly Inspect

Our laboratory receives a wide variety of components, materials, and surfaces for roughness inspection. Typical samples include:

• Machined metal components – turned, milled, ground, and polished surfaces of steel, aluminum, copper, titanium, and their alloys.
• Plastic and polymer components – injection‑molded, extruded, and machined surfaces of PE, PP, PVC, ABS, PA, and PC.
• Ceramic and glass surfaces – for precision optics, bearings, and semiconductor applications.
• Coated and plated surfaces – painted, powder‑coated, electroplated, anodized, and thermally sprayed surfaces.
• Composite and laminate surfaces – for aerospace, automotive, and construction applications.
• Medical device surfaces – implants, surgical instruments, and diagnostic components.
• Automotive and aerospace components – engine blocks, cylinder bores, gear teeth, and turbine blades.
• Prototype and new surface finishes – submitted by manufacturers for validation of surface texture before series production.
• Field‑retrieved components – for failure analysis and remaining life assessment.

Contact Profilometry – Stylus‑Based Roughness Measurement

Contact profilometry uses a diamond stylus that traverses the surface, measuring the vertical displacement of the stylus as it moves across the surface. This method is the most widely used and standardized technique for measuring surface roughness. Our procedures follow international standards and the requirements of the Croatian industrial, automotive, and precision engineering sectors.

• Stylus profilometry measurement (ISO 4287 / ASME B46.1 / HRN EN ISO 4287 / NTC 5700 – for general surface roughness) – we use a calibrated contact profilometer with a diamond stylus (tip radius 2 μm to 5 μm) to measure the surface roughness profile along a specified evaluation length (typically 5 mm to 20 mm). The stylus traverses the surface at a constant speed (typically 0.5 mm/s to 1 mm/s), and the vertical displacement is recorded. We calculate the standard roughness parameters: Ra (arithmetic mean deviation), Rz (average maximum height), Rq (root mean square deviation), Rmax (maximum peak‑to‑valley height), Rsk (skewness), Rku (kurtosis), RSm (mean spacing of profile irregularities), and RΔq (root mean square slope). We report the roughness profile, the measured parameters, the evaluation length, and the measurement uncertainty.
• Roughness measurement on curved surfaces (NTC 5701 – for cylindrical and spherical surfaces) – for curved surfaces (e.g., shafts, bores, and spheres), we use a special probe or a test fixture that allows the stylus to traverse the surface in a controlled manner. We apply a correction factor for the curvature effect and report the corrected roughness values.
• Roughness measurement on small‑diameter bores (NTC 5702 – for confined spaces) – for small‑diameter bores (< 10 mm), we use a miniature stylus probe with a smaller tip radius (1 μm) and a reduced gauge length. We report the roughness values and the measurement limitations.
• Roughness measurement at different orientations (NTC 5703 – for the directional analysis) – we perform roughness measurements in multiple directions (e.g., longitudinal and transverse) to evaluate the anisotropy of the surface texture. We report the roughness values for each direction and the anisotropy ratio.
• Roughness measurement at different temperatures (NTC 5704 – for the thermal effect) – we perform the roughness measurement at elevated temperatures (e.g., 40 °C, 60 °C) using a heated test fixture, to evaluate the effect of temperature on the surface topography. We report the roughness values at each temperature.

Optical Profilometry – Non‑Contact Roughness Measurement

Optical profilometry uses white light interferometry, confocal microscopy, or laser triangulation to measure the surface topography without physical contact. This method is ideal for soft, delicate, or highly reflective surfaces, and it provides a high‑resolution 3‑D representation of the surface. Our procedures follow international standards and the requirements of the Croatian high‑precision, medical device, and electronics industries.

• White light interferometry (WLI) – ISO 25178 / NTC 5710 – for high‑resolution 3‑D surface measurement – we use a white light interferometer to scan the surface and generate a high‑resolution 3‑D topographic map. We measure the 2‑D parameters (Ra, Rz, Rq) and the 3‑D parameters (Sa, Sz, Sq, Ssk, Sku, Spd, and Sdr). We report the 3‑D surface map, the measured parameters, and the areal material ratio.
• Confocal microscopy (NTC 5711 – for the high‑magnification surface imaging) – we use a confocal microscope to capture high‑magnification images of the surface, and we generate a 3‑D surface reconstruction from the stack of images. The roughness parameters and the surface texture are reported. We report the 3‑D surface images and the roughness parameters.
• Laser profilometry (NTC 5712 – for the large‑area scanning) – we use a laser triangulation profilometer to scan the surface over a large area (up to several centimeters) and to measure the surface profile. We report the 2‑D and 3‑D roughness parameters and the surface map.
• Comparative measurement of different optical methods (NTC 5713 – for the method validation) – we perform roughness measurements using multiple optical methods (WLI, confocal, and laser) and compare the results to identify the most appropriate method for the specific material and surface texture. We report the comparison and the method recommendation.
• Measurement of transparent and reflective surfaces (NTC 5714 – for the special materials) – for transparent (e.g., glass, polymer) or highly reflective (e.g., polished metal) surfaces, we use an optical profilometer with a specific light source (e.g., a blue light or a polarized light) to reduce the reflection and to obtain a reliable measurement. We report the roughness values and the measurement conditions.

Roughness Parameters and Interpretation – Quantifying the Surface Texture

The surface roughness parameters provide a quantitative description of the surface texture. Our tests measure a comprehensive set of parameters, and we interpret the results in the context of the specific application (e.g., sealing, friction, wear, coating adhesion, or optical clarity).

• Amplitude parameters (Ra, Rz, Rq, Rmax – NTC 5720 – for the height characterization) – we measure the amplitude parameters (Ra, Rz, Rq, and Rmax) from the roughness profile. The amplitude parameters describe the vertical extent of the surface irregularities. We report the amplitude parameters and the interpretation.
• Hybrid parameters (Rsk, Rku – NTC 5721 – for the shape characterization) – we measure the skewness (Rsk) and the kurtosis (Rku) of the roughness profile. The skewness describes the asymmetry of the profile, and the kurtosis describes the peakedness. These parameters are used to assess the load‑bearing capacity, the wear resistance, and the sealing performance of the surface. We report the Rsk and Rku values and the interpretation.
• Spacing parameters (RSm, RΔq – NTC 5722 – for the lateral characterization) – we measure the mean spacing of the profile irregularities (RSm) and the root mean square slope (RΔq). These parameters are used to assess the density of the surface features, the surface drainage properties, and the friction characteristics. We report the RSm and RΔq values and the interpretation.
• Material ratio curve (Abbott‑Firestone curve – NTC 5723 – for the bearing area analysis) – we generate the material ratio curve (the Abbott‑Firestone curve) from the roughness profile. The curve provides the bearing area as a function of the depth. The material ratio is correlated with the sealing performance, the wear resistance, and the load‑bearing capacity. We report the material ratio curve and the Rpk, Rk, and Rvk parameters.
• Correlation of roughness parameters with the application (NTC 5724 – for the performance‑based assessment) – we correlate the measured roughness parameters with the specific application (e.g., the friction coefficient, the sealing leakage, the coating adhesion, or the optical clarity). The correlation is based on empirical models or on the manufacturer's specifications. We report the correlation and the application‑specific recommendations.

Environmental and Aging Effects on Roughness – Evaluating the Long‑Term Stability

The surface roughness of a component can change over time due to corrosion, wear, erosion, and deposit formation. Our environmental and aging tests evaluate the long‑term stability of the surface finish, ensuring the reliability of the component over its service life in the diverse Croatian climate (coastal, continental, and mountainous).

• Corrosion and erosion exposure test (NTC 5730 – for the simulated service exposure) – we expose the component to a corrosive or erosive environment (e.g., salt spray, acidic solution, or abrasive slurry) for a specified duration (e.g., 7, 14, or 28 days) and then re‑measure the surface roughness. The change in the roughness (in %) is reported. We report the roughness after exposure and the change.
• Thermal aging effect on roughness (NTC 5731 – for the heat‑aged components) – we age the component 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 re‑measure the roughness. The change in the roughness and the formation of any oxide scale are reported. We report the roughness after aging and the oxide condition.
• Water immersion and moisture effect (NTC 5732 – for the moisture‑exposed components) – we immerse the component in water (or a process fluid) for a specified duration (e.g., 7 days) and then re‑measure the roughness. The change in the roughness and the presence of any deposits are reported. We report the roughness after immersion and the deposit condition.
• Chemical exposure effect (NTC 5733 – for the chemically exposed components) – we immerse the component in various chemicals (e.g., mineral oil, 10 % HCl, 10 % NaOH, or a solvent) for a specified duration (e.g., 7 days) and then re‑measure the roughness. The change in the roughness and the surface condition (e.g., etching, pitting) are reported. We report the roughness after chemical exposure and the surface condition.
• Wear and abrasion effect (NTC 5734 – for the mechanical wear) – we subject the surface to a specified number of wear cycles (e.g., by rubbing, sliding, or abrading) and then re‑measure the roughness. The change in the roughness and the wear pattern are reported. We report the roughness after wear and the wear pattern.

Complementary Tests – Hardness, Dimensional Inspection, and Material Verification for Roughness Correlation

To provide a comprehensive assessment of the component's quality and to understand the factors that influence the surface roughness, we perform complementary tests, including hardness testing, dimensional inspection, and material verification.

• Hardness testing (ASTM E18 / NTC 5740 – Rockwell, Brinell, or Vickers) – we measure the hardness of the component material (HRC, HRB, HB, or HV). The hardness is correlated with the wear resistance and the ability to maintain a smooth surface finish. We report the hardness and the correlation.
• Dimensional inspection (NTC 5741 – for the diameter, thickness, and geometry) – we measure the critical dimensions (the diameter, the thickness, the length, and the geometry) of the component using calibrated instruments (e.g., micrometers, calipers, and CMMs). The dimensions are correlated with the roughness. We report the dimensions and the geometry.
• Material identification (FTIR, XRF – NTC 5742 – for the material verification) – we use Fourier‑transform infrared spectroscopy (FTIR) and X‑ray fluorescence (XRF) to identify the chemical composition of the component material and to verify that it matches the specified grade. The material type is correlated with the roughness and the corrosion resistance. We report the material identification and the compliance.
• Metallographic examination (ASTM E3 / NTC 5743 – for the grain size and the microstructure) – we examine the microstructure of the component material (the grain size, the phase distribution, and the inclusion content) using optical microscopy and SEM. The microstructure is correlated with the surface finish and the wear resistance. We report the grain size, the phase distribution, and the inclusion rating.
• Surface defect analysis (NTC 5744 – for the detection of defects) – we use a borescope or a video inspection system to inspect the surface for defects (e.g., cracks, pits, laps, or gouges) that could affect the roughness and the performance. We report the location, the type, and the severity of any defects.

Test Report and Recognition in the Croatian Industrial, Manufacturing, and Engineering Sector

All procedures described are within the scope of our ISO/IEC 17025 accreditation, with equipment calibrated periodically (profilometers, optical profilers, CMMs, and measuring 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 (component type, material, dimensions, and manufacturer).
• Detailed description of the test methods applied (ISO/ASME/HRN EN/NTC standards, test conditions, and measurement parameters).
• Numerical results: roughness parameters (Ra, Rz, Rq, Rmax, Rsk, RSm, Rpk, Rk, Rvk), 3‑D parameters (Sa, Sz, Sq), hardness (HRC/HV), dimensional data, and property retention after environmental exposure (%).
• Graphical data: roughness profiles, 3‑D surface maps, material ratio curves, and roughness vs. application correlation plots.
• Comparative tables against the values specified by the client or against the limits of the relevant standards (ISO 4287, ASME B46.1, ISO 13565, HRN EN ISO 4287, and the requirements of the HZN, Ministarstvo gospodarstva, and Državni inspektorat).
• Photographs of the surface (from the borescope inspection) and the profilometry traces.
• Recommendations for surface finish optimization, material selection, and quality control measures to achieve the required roughness and 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 precision components, machined parts, and surface‑finished products. Additionally, we offer consulting services for the selection of optimal surface finishes, the design of manufacturing processes to achieve the required roughness, and the implementation of quality control programs for surface quality, contributing to the performance, reliability, and longevity of products in the diverse and growing Croatian market, from the automotive and aerospace sectors to the medical device and precision engineering industries.