Overview - ISO 19397:2024 (Ultrasonic film thickness measurement)
ISO 19397:2024 specifies a non-destructive method for determining the film thickness of coatings on metallic and non‑metallic substrates using an ultrasonic gauge. This first edition replaces ISO/TS 19397:2015 and provides updated normative references and an added introduction. The method is based on time‑of‑flight measurement of ultrasonic echoes (A‑scan) from coating interfaces and converts sound travel time to dry film thickness when the sound velocity in each layer is known.
Key technical topics and requirements
- Principle: Uses longitudinal ultrasonic waves and pulse-echo (A‑scan) presentation to resolve reflections from coating interfaces. Film thickness t is calculated from sound velocity v and round‑trip travel time T using d = v · (T/2).
- Apparatus and materials:
- Ultrasonic film thickness measuring device (sensor/probe with delay path)
- Couplant (e.g., water, glycerine, oil) to transmit ultrasound between probe and test object
- Calibration standards and working standards traceable to national standards
- Calibration, adjustment and checking: Defines calibration and adjustment practices, and periodic checking of instrument adjustment as prerequisites for valid results.
- Measurement procedure: Specifies how to acquire and evaluate echoes, handle phase changes (positive/negative half‑waves), and interpret merged echoes when layers are too thin to resolve optically (example: 20 ns time interval ≈ 20 µm coating).
- Environmental and operational factors: Addresses temperature influence on measurements and provides guidance on acceptable conditions.
- Precision and metrology: Includes provisions for determining repeatability and reproducibility limits and reporting measurement uncertainty.
- Reporting: Content requirements for the test report and informational annexes (e.g., personnel competence, precision determination).
Practical applications and users
ISO 19397:2024 is used wherever accurate, non‑destructive film thickness data are required:
- Quality control in paints and varnishes, industrial coatings and finishing lines
- Surface inspection in automotive, aerospace, marine and infrastructure protective coatings
- Field and laboratory NDT (non‑destructive testing) by inspection bodies and third‑party testing labs
- R&D and material characterization for coating manufacturers and formulators
Typical users include coating technologists, NDT technicians, quality engineers, and laboratory staff responsible for calibration and measurement traceability.
Related standards
- ISO 4618 - Paints and varnishes: vocabulary (terminology referenced)
- ISO Guide 99 - International vocabulary of metrology (VIM)
- ISO 2808 (related coating measurement standards) and the withdrawn ISO/TS 19397:2015 (superseded)
Keywords: ISO 19397:2024, ultrasonic gauge, film thickness, coatings, paints and varnishes, non‑destructive testing, A‑scan, calibration, couplant, measurement precision.