🎨 Coating adhesion (cross-cut test)
In short
Paint coating adhesion test by cross-cut method. Classification on scale 0–5 based on degree of coating detachment from substrate. The test is performed according to PN-EN ISO 2409:2020; Incision spacing: 1 mm (coating ≤60 µm), 2 mm (61–120 µm), 3 mm (121–250 µm). The procedure comprises 10 steps (about 16 h 27 min in total); it is used for: Quality control of paint coatings in automotive serial production, Testing KTL (cathodic electrocoating) adhesion to sheet metal, Assessment of powder paint coatings on metal components.
At a glance
- Standard: PN-EN ISO 2409:2020
- Category: Automotive
- Procedure steps: 10
- Total time of stages: 16 h 27 min
- Incision spacing: 1 mm (coating ≤60 µm), 2 mm (61–120 µm), 3 mm (121–250 µm)
- Number of incisions: 6 in each direction (creates 25 squares grid)
- Classification scale: 0 (perfect) to 5 (>65% detachment)
Overview
The cross-cut test is one of the simplest, cheapest, and most widely used methods for assessing adhesion of paint, varnish, and galvanic coatings to substrates. The PN-EN ISO 2409 standard describes the procedure for cutting a grid of rectangular incisions in the coating, reaching the substrate, and then visually assessing the degree of coating detachment.
In the automotive industry, the cross-cut test is a standard control test for KTL (cathodic electrocoating) coatings, base and clear coats, powder paint, and decorative coatings on interior components. It is required by corporate standards (VW TL 226, BMW GS 90010, PSA D24 1312) and in PPAP/ISIR processes when approving new suppliers.
The method involves making six parallel incisions, then six perpendicular incisions, forming a grid of squares. Incision spacing depends on coating thickness: 1 mm (up to 60 µm), 2 mm (61–120 µm), or 3 mm (121–250 µm). After cutting, loose coating fragments are removed using adhesive tape, and the result is visually classified on a six-grade scale (0 — excellent adhesion, 5 — over 65% detachment).
The test is quick (several minutes), low-cost, and does not require specialized equipment — a multi-blade cutter, adhesive tape, and magnifying glass are sufficient. However, it is a destructive test and gives a qualitative (not quantitative) result, which is its limitation compared to pull-off methods (ISO 4624).
Method principle
A grid of rectangular incisions with specified spacing is made in the paint coating, reaching the substrate. A multi-blade cutter (6 blades) is guided perpendicular to the surface with even pressure, creating 25 (5×5) or 36 (6×6) square fields depending on cutter version. Standard adhesive tape (width 25 mm, adhesion force 6–10 N/25 mm) is applied to the cut grid, pressed with a finger, and torn off at 60° angle within 0.5–1 s. Detached coating fragments on tape and in incisions are compared with standard reference tables. The result is expressed as a class from 0 (incision edges perfectly smooth, no detachment) to 5 (detachment >65% of grid area).
Applications
- Quality control of paint coatings in automotive serial production
- Testing KTL (cathodic electrocoating) adhesion to sheet metal
- Assessment of powder paint coatings on metal components
- Verification of decorative coating adhesion on plastic components
- Incoming inspection of components from sub-suppliers (PPAP/ISIR)
- Coating durability testing after accelerated tests (salt spray, UV aging)
- Assessment of anticorrosive coatings in construction and infrastructure
Key parameters
| Parameter | Value |
|---|---|
| Incision spacing | 1 mm (coating ≤60 µm), 2 mm (61–120 µm), 3 mm (121–250 µm) |
| Number of incisions | 6 in each direction (creates 25 squares grid) |
| Classification scale | 0 (perfect) to 5 (>65% detachment) |
| Adhesive tape | Width 25 mm, adhesion force 6–10 N/25 mm according to ISO 2409 |
| Laboratory conditions | 23 ± 2°C, 50 ± 5% RH, conditioning min. 16 h |
| Maximum coating thickness | 250 µm (above — pull-off method according to ISO 4624) |
Standard
- Standard number
- PN-EN ISO 2409:2020
- Title (PL)
- Farby i lakiery — Próba przecinania
- Title (EN)
- Paints and varnishes — Cross-cut test
Step-by-step procedure
-
Sample preparation
Ensure coating is fully cured (according to technical data sheet). Condition sample min. 16 h at 23±2°C, 50±5% RH.
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Coating thickness measurement
Measure coating thickness with gauge near test location. Based on this, select incision spacing: ≤60 µm → 1 mm, 61–120 µm → 2 mm, 121–250 µm → 3 mm.
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Making horizontal incisions
Apply multi-blade cutter to surface. Guide with even motion, with pressure sufficient to cut coating to substrate. Make 6 parallel incisions.
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Making perpendicular incisions
Rotate cutter or sample 90°. Make another 6 incisions perpendicular to first, creating grid of squares.
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Grid cleaning
Gently clean incision grid with soft brush (5 strokes along each diagonal) to remove loose fragments.
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Applying adhesive tape
Cut approximately 75 mm of adhesive tape. Apply to incision grid, pressing with finger without air bubbles. Contact time: 5 min (±30 s).
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Tape removal
Grasp free end of tape. Tear with firm motion at approximately 60° angle from surface within 0.5–1 s.
-
Visual assessment
Compare appearance of incision grid with ISO 2409 standard reference tables. Rate on scale 0–5: class 0 — no detachment, class 5 — detachment >65%.
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Documentation
Record: coating type, thickness, substrate, incision spacing, classification result. Keep tape with detached fragments. Take photo.
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Repetition (optional)
Perform test in at least 3 locations on sample. Report result as worst obtained or median — according to specification requirements.
Required equipment and apparatus
| Equipment | Example | Indicative price |
|---|---|---|
| Multi-blade cross-cut cutter | Elcometer 107, TQC CC3000, BYK-Gardner Cross-Cut 5120 | 800–3 500 PLN |
| Cross-cut adhesive tape | Tesa 4657, Scotch 610, Nichiban CT-24, according to ISO 2409 | 50–150 PLN/roll |
| Illuminated magnifying glass | Magnifier 3×–6× with LED, Elcometer, TQC | 200–800 PLN |
| Coating thickness gauge | DeFelsko PosiTector 6000, Elcometer 456, Fischer FMP30 | 2 000–12 000 PLN |
| Cutter guide template | Steel template with guide groove | 300–800 PLN |
Reagents, media and consumables
| Reagent | CAS | Details |
|---|---|---|
| Test adhesive tape | — | Compliant with ISO 2409, width 25 mm, adhesion force 6–10 N/25 mm, roll 33–66 m |
| Surface cleaning liquid | — | Isopropanol or acetone for degreasing before test (optional) |
| Replacement cutter blades | — | Set of 6 hardened steel blades, replace every 50–100 tests or when dull |
Health and safety (OHS)
- Multi-blade cutter — sharp blades, risk of cuts, store with cover
- Safety glasses during cutting (coating/substrate fragments)
- Protective gloves recommended when handling samples with sharp edges
- Samples after test may have sharp incision edges — caution during disposal
Frequently asked questions
Which standard describes this test?
The test is performed according to PN-EN ISO 2409:2020 — “Paints and varnishes — Cross-cut test”.
How does this method work?
A grid of rectangular incisions with specified spacing is made in the paint coating, reaching the substrate. A multi-blade cutter (6 blades) is guided perpendicular to the surface with even pressure, creating 25 (5×5) or 36 (6×6) square fields depending on cutter version.
What is the measuring range and accuracy?
Incision spacing: 1 mm (coating ≤60 µm), 2 mm (61–120 µm), 3 mm (121–250 µm); Number of incisions: 6 in each direction (creates 25 squares grid); Classification scale: 0 (perfect) to 5 (>65% detachment); Adhesive tape: Width 25 mm, adhesion force 6–10 N/25 mm according to ISO 2409.
How long does the test take?
The times given for the individual stages add up to approximately 16 h 27 min. The procedure comprises 10 steps.
What equipment is required?
Multi-blade cross-cut cutter, Cross-cut adhesive tape, Illuminated magnifying glass, Coating thickness gauge, Cutter guide template. Indicative cost of the core instrument (Multi-blade cross-cut cutter): 800–3 500 PLN.
Where is this test used?
Quality control of paint coatings in automotive serial production; Testing KTL (cathodic electrocoating) adhesion to sheet metal; Assessment of powder paint coatings on metal components; Verification of decorative coating adhesion on plastic components; Incoming inspection of components from sub-suppliers (PPAP/ISIR); Coating durability testing after accelerated tests (salt spray, UV aging); Assessment of anticorrosive coatings in construction and infrastructure.
What safety precautions apply?
Multi-blade cutter — sharp blades, risk of cuts, store with cover; Safety glasses during cutting (coating/substrate fragments); Protective gloves recommended when handling samples with sharp edges; Samples after test may have sharp incision edges — caution during disposal.
Which laboratory can perform this test?
The test is performed by laboratories accredited to ISO/IEC 17025. On LabCoda you can find them by the standard number PN-EN ISO 2409.