Performance of an adhesion test on paint using a grid comb (ISO 2409 standard before and after immersion)
Description
The cross-sectional adhesion test according to ISO 2409 is one of the most widely used methods for evaluating the adhesion of a painted coating to its substrate. It determines whether a paint, varnish, or technical coating is properly bonded, or if there is a risk of flaking, delamination, or loss of integrity during use. This analysis is particularly essential in the packaging, materials, and polymers sectors, as well as in industries where the durability of coated surfaces is a critical performance factor. The version performed before and after immersion adds an accelerated aging dimension, simulating the coating's exposure to humidity, industrial liquids, or corrosive atmospheres.
Principle and operation of the grid method
The ISO 2409 test involves creating a precise grid on the painted surface using a standardized comb, producing a series of regular cuts that incise the coating. After the grid is created, a reference adhesive tape is applied and then removed in a controlled motion. Visual assessment of the coating's detachment allows the adhesion to be classified on a scale of 0 to 5, where 0 corresponds to perfect adhesion and 5 to severe detachment. The sharpness of the incision edges, the amount of material removed, and the overall appearance of the grid are carefully examined, often using a binocular microscope to improve readability. This method, while seemingly simple, requires significant rigor in sample preparation, comb selection, cut alignment, and standardization of test conditions.
Pre- and post-immersion testing: interest and interpretation
Comparing adhesion before and after immersion is a crucial step in evaluating a coating's resistance to humid or aggressive environments. Immersion can be performed in water, saline solutions, technical fluids, or controlled environments, depending on customer requirements. After the defined exposure time, the cross-section test is repeated. A significant degradation in the adhesion classification reveals the coating's sensitivity to moisture, corrosion, or liquid penetration at the interfaces. This test is widely used for quality control of finished products (metal packaging, coated plastic parts, industrial components), as well as in R&D to compare different paint formulations or improve coating durability.
Industrial importance and quality control
In the materials, polymers, and packaging sectors, coating adhesion determines product durability and safety. Insufficiently adherent paint can lead to aesthetic defects, surface contamination, loss of corrosion protection, or mechanical weakening. For plastic parts, ISO 2409 validates surface treatments, preparation (sandblasting, plasma, primer), and the compatibility between the polymer and the applied coating. In metal or composite packaging, the test ensures the durability of internal and external coatings, particularly when they come into contact with food liquids or humid environments. Manufacturers also use this test to audit suppliers, control production batches, or qualify new formulations.
Analyzed matrices
The cross-section adhesion test can be applied to a wide variety of substrates and coatings: industrial paints, varnishes, lacquers, anti-corrosion coatings, protective layers, coated polymers, metal packaging, injection-molded plastic parts, coated technical films, composite materials, and rigid or flexible substrates. Any surface covered with a coating that can flake or peel is a suitable matrix for this test.
Added value YesWeLab
Thanks to a network of laboratories specializing in coating conformity testing, YesWeLab identifies the most suitable partner based on your product, film thickness, substrate type, and desired immersion conditions. Our partner laboratories, often ISO 17025 and COFRAC certified or accredited, guarantee strict application of the ISO 2409 standard and the reproducibility of results. Our scientific team assists you in defining the protocol, analyzing the results, and selecting additional tests if there is any doubt about the cause of an adhesion defect. Since 2020, manufacturers, formulators, and packaging companies have entrusted us with their samples via our digital platform to optimize their quality control and secure their product development.
Related analyses in the YesWeLab catalog
To complete this adhesion test, the following services are recommended:
