Overview
ISO/TS 19397:2015 - "Determination of the film thickness of coatings using an ultrasonic gage" (ISO) defines a technical specification for measuring coating film thickness on metallic and non‑metallic substrates using an ultrasonic gauge. The method is based on recording ultrasonic pulse echoes (A‑scan) and converting measured time of flight and known sound velocities into film thickness values. The document covers principle, apparatus, calibration, measurement procedure, temperature effects, precision and reporting.
Key topics and technical requirements
- Measurement principle: Determination of single layer thicknesses from echo time intervals (time of flight) and known sound velocity using t = v · (T/2).
- Ultrasonic signals and A‑scan: Use of longitudinal ultrasonic pulses and A‑scan displays to identify echoes from layer interfaces; interpretation must account for phase changes where reflection coefficients are negative.
- Apparatus and couplant: Requirements for an ultrasonic sensor (piezoelectric probe plus delay path), evaluation unit, and suitable couplant (liquid or gel) to ensure acoustic contact.
- Calibration and adjustment: Calibrate per manufacturer instructions; use working/certified calibration standards that approximate the test object (substrate, coating system, thickness range). Determination of sound velocity using representative test specimens is required.
- Checking and verification: Routine checks after power‑up, and when coating system or substrate changes; guidance for repeatability and reproducibility assessment (precision discussed, Annex B).
- Influencing factors: Consideration of temperature effects, acoustic impedance mismatches, thin‑film echo overlap, and curved surfaces that can reduce detectable reflections.
- Documentation: Test reporting requirements and informative annexes covering personnel qualification (Annex A) and precision determination (Annex B).
Applications and users
ISO/TS 19397:2015 is practical for:
- Quality control in paint and coating application (automotive, aerospace, marine, industrial equipment)
- Non‑destructive testing (NDT) in manufacturing and maintenance where destructive sectioning is undesirable
- Coating laboratories validating coating thickness without destructive sampling
- Inspectors and technicians using ultrasonic gages for on‑site or lab measurements
Typical users: coating engineers, NDT technicians, quality managers, third‑party inspectors, and calibration laboratories.
Related standards
- ISO 4618 - Paints and varnishes - Terms and definitions (normative reference)
- Relevant normative references cited within the specification: EN 1330‑4:2010 (ultrasonic NDT terms) and ISO/IEC Guide 99:2007 (calibration terminology)
Keywords: ISO/TS 19397:2015, ultrasonic gage, film thickness, coatings, A‑scan, time of flight, couplant, calibration, acoustic impedance, coating inspection.