The digital pull-out adhesion tester (such as the PositTestAT series) evaluates adhesion by quantifying the peel strength between the coating and the substrate, and is widely used in fields such as coatings, anti-corrosion, aerospace, etc. The following are its standard testing procedures and key considerations:
1、 Preparation before testing
Equipment inspection
Confirm that the tester has sufficient power (or connected to a stable power supply), and that the display screen, sensors, loading rod, and other components are not damaged.
Check if the hinge connectors, adhesives (such as two-component epoxy adhesive or cyanoacrylate adhesive), and cutting tools (such as specialized cutting knives or surgical knives) are complete.
Select the appropriate test column based on the coating type (such as aluminum alloy or steel, typically with a diameter of 20mm).
sample preparation
Surface treatment: Clean the testing area, remove oil stains, dust, or loose coatings (can be wiped with solvent and dried).
Cutting samples:
Use a cutting tool to cut through the coating along the edge of the test column to the substrate, forming a cross shaped incision (with a spacing of about 3-5mm between incisions to ensure stress concentration during peeling).
For thick coatings (>500 μ m), they need to be sanded to a uniform thickness in advance.
Bonding test column:
Apply adhesive evenly at the bottom of the test column and cure according to the instructions (e.g. epoxy adhesive needs to be cured at room temperature for 24 hours or accelerated by heating).
After curing, check that there are no bubbles or gaps on the bonding surface to ensure complete contact with the coating.
environmental control
The temperature of the testing environment should be 23 ± 2 ℃, and the humidity should be ≤ 65% to avoid high temperature or high humidity affecting the performance of the adhesive.
If testing on site, environmental conditions (temperature, humidity) need to be recorded for reference.
2、 Testing process
Equipment installation
Fix the tester onto the test column through the hinge connector, ensuring that the loading rod is aligned with the axis of the test column.
Adjust the zero point of the device: Press the "Zero" button to display "0.0MPa" on the screen (or "0.0psi" according to the unit setting).
load test
Uniform loading: Pull the test column at a constant speed of 0.7MPa/s (or the preset speed of the equipment) until the coating peels off or reaches the upper limit of the equipment range.
Data recording:
The display screen shows the real-time tensile value (unit: MPa or psi) and records the maximum tensile value (F_max).
If the coating is peeled off in layers, record the peeling force and failure mode of each layer (such as peeling between coatings, peeling between coatings and substrate).
Destruction Mode Analysis
Observe the characteristics of the peeling surface and classify it according to standards (such as ISO4624 or ASTMD4541):
Class A: Cohesive failure of the coating (fracture of the coating itself).
Class B: Interface damage between coating and substrate.
Class C: Cohesive failure of substrate (rare, requiring re evaluation of testing methods).
Take photos of the peeled surface as attachments to the test report.
3、 Key precautions
safe operation
Wear protective goggles and gloves to prevent adhesive from coming into contact with the skin or eyes.
Stay away from crowds during testing to avoid injury caused by broken or flying test columns.
error control
Ensure that the test column is perpendicular to the coating to avoid lateral forces affecting the results.
Regularly calibrate equipment (recommended once a year) to ensure sensor accuracy.
Special case handling
Thin coating test: If the coating thickness is less than 50 μ m, a micro test column (such as a diameter of 10mm) or a cross grid method should be used to assist in evaluation.
Flexible substrate: such as plastic or rubber, special fixtures should be used to prevent substrate deformation from affecting the results.
High temperature/corrosive environment: Clean the equipment immediately after testing to prevent adhesive residue or corrosion.
4、 Maintenance and upkeep
Clean the test column and connector after each test to remove any residual adhesive.
When stored for a long time, remove the battery (if removable) and place it in a dry environment.
Regularly check the accuracy of the equipment (such as verifying the tension sensor with standard weights).
By standardizing operations and strictly recording, the accuracy and reliability of the test results of the digital pull-out adhesion tester can be ensured, providing a scientific basis for coating quality evaluation.