Reduction of corrosion protection properties of organic coatings due to abrasive damage produced by natural sands

In many applications, the protective properties of organic coatings against corrosion require good resistance to abrasion. Mechanical damage can locally result in the reduction of the protective properties of paints.This work focuses on the evaluation of abrasion damage produced by sands on organic coatings, using an electrochemical test and a modified Taber test apparatus. The abrasive media were different natural sands, which were selected from seashores and deserts. These were chosen in function of the dimension of the particles, their morphology and chemical composition.The damage caused by the abrasive sands and the resulting reduction of the barrier effect were manifested and strongly dependent on the characteristics of the sands. In particular, the aggressiveness increased with the grain dimensions and with the reduction of the content of calcite in the sand. The desert sands, which had rounded grains, exhibited lower abrasiveness than the sands whose grains had sharp edges. The less aggressive sands lead to a progressive reduction of the protective properties, with a reduction of the thickness with an uniform track on the worn surface; on the other hand, the more abrasive sands had a tendency to create non uniform tracks with larger defects.