PPGI steel sheet need to have various properties of the general coating. And the film of coil coating also need to withstand deep drawing, bending, drilling, bite and other post processing. Therefore, the requirements of flexibility is higher than the traditional coating. The representative indexes are cup drawing, impact, T bend, adhesion and so on.
PPGI steel sheet cupping test is to evaluate the performance of cracking resistance or resistance to separation from the metal substrate after the coatings of the paints, varnishes and related products are gradually deformed under standard conditions. CAMELSTEEL commonly use this test to check the coating flexibility of color coated steel sheet.
The test device of cupping test is cupping test instrument. During the test, the cup punch test machine will take the punch push-out the the reverse side of the sample with the constant speed, stamping for the required depth to observe whether the coating cracking or falling off from the substrate to assess the ability of the coating in resistant to cracking or shedding.
2. Scratch resistance test
Scratch resistance test is mainly used for scratch resistance identification of the coating in insulation color coated steel sheet. In the test, the scratch instrument will utilize the steel needle with a certain weight to snail in the coating surface of ppgi steel sheet in a certain load. If the steel needle broken coating, between the needle and the steel plate or strip will show it’s conductive.
Use the maximum load of the steel needle under a certain weight can damage the coating. Or not to evaluate the coating scratch resistant ability of the ppgi steel sheet.
Scratch resistance experiments usually define the scratch resistance of the coating in two ways. One way is to determine if it can pass under a fixed load. Another method is to incrementally increase the weight of the load weight to repeat the experiment. Until the maximum weight which can not damage the coating can be find out.
In the former method, if there at least two of the three tests pass the test are the test result, and the latter test method uses the arithmetic mean value of the maximum weight load at three different positions as the test result.