Adhesion is the soul of measuring industrial coating quality. If adhesion fails to meet the standard, even the best anti-corrosion performance is meaningless. As a professional industrial coating manufacturer, we provide you with an in-depth analysis of the operation procedure and rating criteria of the internationally recognized "cross-cut test", teaching you how to scientifically evaluate the adhesion of the paint film.
In the field of industrial coating, we often say, "A weak foundation leads to total collapse." The adhesion of the paint film is this "foundation." If the paint film cannot firmly grip the substrate, it will soon peel, flake, and lose its anti-corrosion protection. Today, as an industrial paint manufacturer, let's talk about the most intuitive and commonly used testing method—Cross-Cut Test.
1. Basic principle of the cross-cut method
The cross-cut method involves using a cross-cut tester or a single-edged blade to make vertical and horizontal intersecting cuts on the coating film to form multiple square grids, then applying and peeling off adhesive tape to observe the detachment of the coating within the grid areas.
2. Standard Operating Procedure (refer to ISO 2409 or ASTM D3359)
- Spacing selection: Select the spacing according to the film thickness. Usually on hard substrates, for film thickness $< 60mu m$ use 1mm spacing; for $60-120mu m$ use 2mm spacing.
- Vertical cutting: Use a professional cross-cut tester to evenly and continuously cut through the paint film to the substrate at a constant speed, creating a "well"-shaped grid.
- Cleaning and Taping: Sweep away debris with a soft-bristle brush, firmly apply standard test tape to the cross-cut area, then steadily peel it off at an angle close to 60° within 0.5–1 second.
3. Rating Criteria (ISO Grade Table)
- Level 0 (Highest): The cut edges are completely smooth, with no detachment inside the grid.
- Level 1: Small flakes of paint film are detached at the intersections of the cuts, but the damaged area does not exceed 5% of the cross-cut area.
- Level 2: Chipping at edges and intersections, with damaged area between 5% and 15%.
- Grade 3-5: Large-scale peeling occurs, indicating that the adhesion is seriously substandard, and the substrate treatment or product compatibility must be re-checked.
4. Key Factors Affecting Adhesion
- Surface cleanliness: Residual oil and rust that have not been thoroughly removed are the "killers" of adhesion.
- Improper pairing: The polarity of the primer and topcoat does not match, leading to failure of interlayer adhesion.
- Curing degree: Testing before the paint film has fully reacted and cured often yields inaccurate results.
Conclusion:
Every qualified batch released from the factory must withstand the cross-cut test. We insist on letting the data speak, ensuring that every pail of paint can "take root" on the surface of your equipment and provide long-lasting protection.