Overview
ISO 17872:2019 - Paints and varnishes - Guidelines for the introduction of scribe marks through coatings on metallic panels for corrosion testing - is an ISO guideline describing how to introduce controlled damage (scribe marks) through organic coatings on metallic test panels prior to corrosion testing. It applies to coating systems with dry film thicknesses of less than 500 μm and covers steel, galvanized steel, aluminium alloys and magnesium alloys (but not electroplated metal or clad aluminium). The document is based on a collaborative trial and is intended as a guideline only - no subsequent corrosion testing was performed within the trial to validate scribe suitability.
Key technical topics and requirements
- Scope and materials: Coated panels for steel, galvanized steel, aluminium and magnesium alloys; excludes electroplated/clad aluminium. Applicable for coatings < 500 μm.
- Scribe shapes and layouts: Typical surface shapes include X, single line, T, L and diagonal scribes; dimensions and edge placement (minimum 20 mm from panel edge) are illustrated.
- Cross-sectional profiles: Scribes commonly produce V- or U-shaped cuts. The guideline specifies geometry relations (e.g., for V: a > b > c) and minimum surface width b > 0.2 mm. Automated machines may produce rectangular sections with dimensions typically > 0.5 mm.
- Scribing length: Recommended line lengths are typically 50–70 mm, long enough to exceed expected corrosion creep.
- Orientation and substrate effects: Scribe orientation (horizontal, vertical, diagonal) affects salt deposition and corrosion progression; milled/rolled aluminium panels should receive two scribes in different orientations to assess rolling-direction effects.
- Procedure and tools: Use a metal rule for straightness; clean debris and inspect with ×5–×10 magnification; verify and maintain scribing tool sharpness. Annex A lists commonly used scribing tools; Annex B shows how different tools can change corrosion outcomes.
- Reporting: Test report must record substrate, surface preparation, coating system and thickness, scribing tool, scribe shape/dimensions/orientation, referenced standards (ISO 17872:2019), and any deviations or anomalies.
Practical applications and who uses it
- Corrosion testing labs and quality control teams in coatings and metal manufacturing use ISO 17872 to standardize how intentional damage is introduced before accelerated corrosion tests (e.g., salt-spray).
- R&D and formulation teams use the guideline when comparing coating adhesion, durability and failure modes after exposure.
- Third-party testers and auditors adopt the recommendations to improve reproducibility and traceability of scribe-based corrosion assessments.
Related standards
- ISO 4618 - Paints and varnishes: terms and definitions
- ISO 12944-6 and ISO 12944-9 - Corrosion protection of steel structures (referenced for hot-dip galvanized requirements)
- ISO 4628-8 - Evaluation of degree of corrosion (used for scribe evaluation examples)
Keywords: ISO 17872:2019, scribe marks, corrosion testing, paints and varnishes, coating scribing, metallic panels, scribing tools, salt-spray testing.