Overview
ISO 6860:2006 defines an empirical bend test using a conical mandrel to assess the resistance of paints, varnishes and related coating systems to cracking and/or detachment from metal substrates when subjected to bending under standard conditions. The method applies to single- or multi-coat systems (each coat may be tested individually or as a complete system) and is intended for quality control, formulation development and compliance verification.
Key Topics
- Scope and purpose: Evaluates mechanical integrity of coatings on metal substrates when bent around a truncated cone.
- Apparatus: A truncated-cone mandrel with specified dimensions (small diameter d0 = 3.1 ± 0.1 mm, large diameter d1 = 38 ± 0.1 mm, length l = 203 ± 3 mm) mounted horizontally with a draw bar and panel clamp.
- Test panels and substrates: Panels generally conform to ISO 1514 (burnished steel, tinplate or soft aluminium), nominal size about 75 mm × 150 mm and maximum thickness 0.8 mm. For aluminium the rolling direction is specified relative to the cone axis.
- Conditioning and thickness: Panels are dried/stoved and conditioned at (23 ± 2) °C and (50 ± 5) % RH for at least 16 hours. Dry film thickness is measured per ISO 2808.
- Procedure essentials: Tests are performed in triplicate. Panels are clamped coated-side to the draw bar, then bent 180° over the mandrel in 2–3 s. Crack extent is examined immediately (10× lens or unaided eye) and measured from the small end of the cone.
- Precision metrics: Repeatability (r) = 23 mm and reproducibility (R) = 46 mm for mean results of triplicates.
Applications
ISO 6860:2006 is widely used by:
- Quality control laboratories assessing coating toughness and adhesion under deformation.
- Formulation and R&D teams comparing resistance to cracking for new paint or varnish systems.
- Manufacturers and specifiers verifying compliance with product specifications or contractual requirements.
Practical value includes rapid, repeatable assessment of coating performance on representative metal substrates and clear reporting criteria for pass/fail or comparative evaluation.
Related Standards
This conical mandrel bend test is part of a family of empirical deformation tests for coatings. Key related documents include:
For reporting, include identification of the product, reference to ISO 6860:2006, test conditions, mean result (mm), any deviations and the operator name and date. This ensures traceable, actionable test outcomes for coating evaluation and decision-making.
