Coating in practical application often by sand friction or mechanical wear of other media, the wear-resisting performance of the coating refers to the ability of the coating against external friction, namely coating hardness, adhesion and cohesion comprehensive effect, but also with the substrate type, surface treatment and coating drying process temperature and humidity.
There are many methods to test the wear resistance of coating, the principle of which is basically to simulate the damage model of coating in practical application.For example, rotating rubber grinding wheel method is used to simulate the wear and damage of leather shoes to floor coating, and pig bristle brush is used to simulate the cleaning method of construction coating after contamination.
The wear resistance evaluation of coating by falling sand method is mainly to simulate the wear resistance of coating exposed to wind and sand for a long time.The principle of this method is to let a certain size of sand and gravel through a fixed inner diameter of the tube from the specified height to the test plate, until wear until exposed to the substrate.The amount of sand consumed is then measured and the result is expressed in the standard amount of sand used per coating thickness.
falling sand abrasion test method, however, wear-resisting test operation is simple, but the test time is longer, and the test result reproducibility is poor, and test the selected abrasive has significant influence on test results, this is because the channels from different sources of abrasive, even if meet the size requirements of relevant standards, but the differences between abrasive particle morphology characteristics, physical properties of stability, consistency test result of comparability and poor reproducibility.Therefore, in order to make the test results as comparable as possible, the operator should ensure that:
1. Use abrasive from the same source and coarsely screen and dry before use
2. Perform sand outflow velocity calibration in strict accordance with the standard: ensure that the inner part of the sand bundle falls exactly at the center of the sand flow, and the outflow velocity is 2L within 21S ~ 23.5s
3. Calibration of abrasion circle: the center of the maximum abrasion zone shall be on the center line of the abrasion elliptic axis and within 14mm ~ 17mm from the upper end.