Performance requirements and testing of pressure plate anti-corrosion coating
- What are the main performance requirements for the anti - corrosion coating of pressing plates?
Corrosion resistance is the core. It should be able to resist red rust for more than 500 hours in the salt spray test, and higher requirements (more than 720 hours) are required in coastal or humid areas to resist environmental erosion. The adhesion is strong. The adhesion between the coating and the pressing plate substrate should be ≥5MPa (cross - cut test) to avoid falling off during installation or use, which affects the anti - corrosion effect. It has good wear resistance and can withstand friction with the rail. The wear amount should not exceed 50μm under specified test conditions (such as 1000 times of friction).
- What are the common types of anti - corrosion coatings for pressing plates?
Zinc coating is widely used, with a thickness of ≥85μm, good corrosion resistance and moderate cost, which is mostly used for ordinary railway pressing plates. The thickness of epoxy coating is usually 60 - 100μm, with strong chemical corrosion resistance, suitable for industrial pollution areas or acid - base environments, but its wear resistance is slightly lower than that of zinc coating. Zinc - aluminum composite coating (such as Dacromet) has a thickness of 5 - 10μm, excellent salt spray resistance (more than 1000 hours), environmental protection and chromium - free, suitable for areas with high environmental protection requirements.
- How to test whether the performance of the anti - corrosion coating meets the standard?
The salt spray test is a common method. The coated pressing plate is placed in a 5% NaCl salt spray box, and the rusting situation is observed according to the specified time. No red rust or rust area ≤5% is qualified. The adhesion test adopts the cross - cut method. A knife is used to cut a cross grid on the coating. No coating falls off after tape pasting is qualified, or the adhesion value is directly measured by the pull - off method. The thickness test uses a coating thickness gauge, and the average value of multi - point measurement should be within the specified range (such as galvanizing ≥85μm).
- What are the differences in the service life of anti - corrosion coatings in different environments?
In dry inland areas, the service life of zinc coating is usually 8 - 10 years, and that of epoxy coating can reach 10 - 12 years. In coastal humid areas, the service life of zinc coating is shortened to 5 - 7 years, while that of zinc - aluminum composite coating can still reach 8 - 10 years due to better salt spray resistance. In industrial pollution areas (containing acid and alkali), the service life of epoxy coating is 3 - 5 years longer than that of zinc coating, and it is more resistant to chemical corrosion.
- How to repair the coating after damage?
For small - area damage (such as diameter ≤5mm), repair paint can be used. First, clean the damaged part (derusting, degreasing), and apply repair paint compatible with the original coating, with a thickness not less than the original coating. For large - area damage (more than 10%), overall re - spraying is required to ensure consistent coating performance. The repaired pressing plate needs to be re - tested for local performance (such as adhesion) before use.