ISO 1518-1:2023

Overview

ISO 1518-1:2023 - Paints and varnishes - Determination of scratch resistance - Part 1: Constant-loading method specifies a standardized laboratory test to quantify how a single coating or a multi-coat paint/varnish system resists penetration by a loaded scratch stylus. The method can be used as a pass/fail test at a single specified load or as an assessment test by increasing loads to determine the minimum load that causes penetration.

Key topics and technical requirements

• Test principle: A hemispherical stylus is drawn across the coating at a constant speed under a specified load until penetration occurs or the scratch is complete.
• Loads and increments: Test load range 1 N to 20 N, adjustable in 0.5 N steps; maximum permissible error 0.2 N.
• Stylus geometry: Defined hemispherical tip types and sizes (hard-metal HM3.0, HM1.0, HM0.75, HM0.5 and synthetic-ruby SR1.0, SR0.5 with diameters ±0.01 mm).
• Apparatus and motion: Panel moved relative to stylus at (35 ± 5) mm/s; minimum scratch length 40 mm; lowering ramp angle (12.5 ± 2.5)°.
• Test panels and substrate: Conductive metallic panels 0.7–1.0 mm thick, preferably 200 × 100 mm, prepared per ISO 1514.
• Conditioning and environment: Drying/aging per manufacturer; condition at (23 ± 2) °C and (50 ± 5) % RH for ≥16 h before testing.
• Evaluation: Visual inspection with at least ×4 magnification; optional electrical indicating device for penetration (not suitable for paints with conductive pigments or non-metallic substrates).
• Procedures:
  • Pass/fail: three repeats on each of two panels (six runs total).
  • Minimum load: start below expected failure load, increase until penetration; report lowest of three determinations.
• Reporting: Include coating application method, drying/stoving conditions, film thickness (per ISO 2808), and test parameters.

Practical applications

• Quality control and batch acceptance for industrial coatings, automotive finishes, furniture lacquers, protective paints and varnishes.
• Performance benchmarking for coating development and R&D to compare scratch resistance across formulations.
• Specifying acceptance criteria in procurement and conformity assessment (useful when a specific load threshold is required).
• Failure analysis and durability testing of multi-coat systems where intermediate-coat penetration behavior matters.

Who should use this standard

• Coating and varnish manufacturers and formulators
• Independent test laboratories and QA/QC teams
• Automotive, aerospace, marine and architectural specifiers
• Coatings R&D and product development engineers
• Certification bodies and procurement/spec writers

Related standards

• ISO 1518-2 (other scratch methods) and ISO 12137 (curved stylus method)
• ISO 1513, ISO 1514, ISO 2808, ISO 4618, ISO 13076, ISO 15528 - referenced for sample preparation, panels, film thickness, terminology, lighting and sampling.

Keywords: ISO 1518-1:2023, scratch resistance, constant-loading method, paints and varnishes, scratch stylus, pass/fail test, minimum load, coating penetration, test standard.