1. Coating Thickness Inspection
Tool: Magnetic thickness gauge (suitable for metal cans).
Method: Measure the current coating thickness and compare it with the original design thickness.
Failure Criterion: If the thickness decreases by more than 50%, it indicates that the anti-corrosion layer is severely damaged and needs to be refurbished.
2. Adhesion Test
Tool: Pull-out adhesion tester.
Method: Apply a vertical tensile force to the can surface and measure the strength required for the coating to detach.
Failure Criterion: If the adhesion strength is less than 5 MPa, the coating is prone to peeling off, indicating anti-corrosion failure.
3. Appearance and Defect Inspection
Visual Inspection:
Cracks and Chalking: Cracks extending to the primer, network cracks, or severe chalking appear on the paint surface (the gloss cannot be restored by rubbing with a finger).
Blistering and Peeling: The paint film blisters, bubbles, or the peeling area exceeds 10% of the total area.
4. Tap and Listen: Gently tap the coating with a rubber mallet. A hollow sound indicates that the coating has detached from the tank body.
5. Rust Prevention and Corrosion Inspection:
Rust Inspection: Observe under the paint film or at welds and joints for rust spots or patches. If the area of spot or flaky rust exceeds 5%, the anti-corrosion treatment has failed.
Electrical Spark Detection: Use an electrical spark detector to check the paint film for pinholes or leakage points. If leakage is found, repair is necessary.
6. Environmental and Usage Factors:
Environmental Impact: Long-term exposure to humid environments, rain (for water-spraying tanks), or environments with large temperature differences will accelerate the aging of the anti-corrosion coating.
Usage Conditions: Highly corrosive media inside the tank (such as acids or alkalis) or frequent fillings will shorten the anti-corrosion cycle.
Comprehensive Judgment and Recommendations:
Regular Inspection: It is recommended to conduct a comprehensive inspection at least once a year, focusing on welds, joints, and the bottom, which are prone to corrosion. Professional Assessment: For large or critical storage tanks, it is recommended to commission a professional organization to conduct non-destructive testing and assessment.
Timely Repair: Once signs of corrosion failure are detected, surface treatment and recoating should be carried out immediately to prevent further corrosion.
