Reduction on protective properties of organic coatings produced by abrasive particles

Mechanical damage can significantly decrease the protective properties of organic coatings. This paper focuses on the common test procedure used for producing simulated ‘three body’ abrasion of surfaces. In these tests rubber wheels are used to move abrasive sands across the sample surface causing abrasion. The mass loss, the decrease in coating thickness, and parameters obtained from the electrochemical measurements are used to evaluate the decrease of protection caused by the abrasion of the coated surface. The imposed weights and abrasive grain size are considered. The aim of this study is to simulate the abrasion degradation caused by abrasive sands and use electrochemical methods to evaluate the decrease in protection shown by a polyester powder coating on steel. In a ‘three body’ abrasion process the measures of mass loss and reduction of the thickness was proved to give limited information to evaluate the actual decrease of the protective properties, while electrochemical measurements allowed to obtain information that can better quantify the damage. In general, fine abrasive particles can give rise to a progressive decrease of protective properties of the coating, whereas coarse particles create large defects in the film which allow rapid corrosion phenomena in the substrate, after few cycles.