Wear 265 (2008) 1820–1825 Contents lists available at ScienceDirect Wear journal homepage: www.elsevier.com/locate/wear Comparison of different abrasion mechanisms on the barrier properties of organic coatings Y. Reyes-Mercado a,b,∗ , S. Rossi a , F. Deflorian a , M. Fedel a a Department of Materials Engineering and Industrial Technologies, University of Trento, via Mesiano 77, 38050 Trento, Italy b Facultad de Qu´ ımica, Universidad Nacional Aut´ onoma de M´ exico, UNAM, Mexico article info Article history: Received 28 June 2007 Received in revised form 9 April 2008 Accepted 30 April 2008 Available online 24 June 2008 Keywords: Paint tribology Taber test Falling abrasive test Organic coating abstract Since the loss of properties of organic coatings due to abrasion is of primary importance in the material performance, the reduction of barrier properties of organic coatings due to abrasion is studied by electro- chemical impedance spectroscopy. The damage of organic coatings caused by abrasion impact of different abrasive materials and abrasion as a result of rubbing aggressive agents against the coating surface is ana- lyzed by environmental scanning electron microscopy (ESEM). The falling abrasive test induces a decrease of coating thickness that can be detected by the thickness gauge and capacitance measurements and it is the main responsible of the loss of coating properties. On the other hand, Taber Abraser test creates scratches by which the protection properties are reduced. © 2008 Elsevier B.V. All rights reserved. 1. Introduction The damage of a surface as a result of rubbing something hard against it is called abrasion. The resistance of an organic coating to support the action of abrasive agents is of primary importance in many applications. Specially, the loss of barrier properties due to the impact of tiny solid or by the action of a slurry containing abrasive particles is a phenomenon of great relevance in automo- tive, naval, military, agricultural and aircraft applications, among others [1,2]. The presence of dust and other solid particles may also seriously diminishes the effectiveness of an organic coating as well as the lifetime. Given the importance of the reduction of protection properties due to the abrasion, many laboratory tests have been developed in order to simulate the operation conditions of the material [3,4]. Within these normalized tests, the Taber Abraser [5] is usually employed to determine the capacity of a coating to resist the action of abrasive agents that are pressed against the coating surface by turning wheels. Typically, the mass loss divided by the number of cycles is reported as the wear index, in addition to the thickness loss. The abrasion may be caused by grinders usually composed of a rubber matrix with tungsten carbide particles or by abrasive ∗ Corresponding author. Permanent address: Facultad de Qu´ ımica, Universidad Nacional Aut ´ onoma de M ´ exico, UNAM, 04510 M´ exico, D.F., Mexico. Tel.: +52 55 91 75 82 69. E-mail address: yurirm@lycos.com (Y. Reyes-Mercado). particles pressed against the coating surface with the aid of rubber wheels [6]. On the other hand, to simulate the damage produced by the impact of solid particles, it is possible to use different experimen- tal devices. In some cases the abrasive particles are accelerated by using a flow of compressed air [7], however, it is also possible to let the abrasive fall under gravity. In this contribution the latest test is used because of the simple geometry of the experimental device, which is actually normalized [8]. According to this method, the abrasion resistance is calculated by the amount of abrasive (in L) employed to remove the coating in an area of approximately 4 mm 2 divided by the initial thickness of the film. As mentioned before, these methods do not provide additional information about the decrease of protection properties. Moreover, the results depend on the operator and there is low reproducibil- ity [9]. However, if they are combined with more sophisticated methodologies it is possible to extract valuable information about the degradation process and obtain reliable predictions of the mate- rial performance. This is the case of the electrochemical impedance spectroscopy (EIS), which is widely used to study the properties of organic coatings under different conditions [10]. One can esti- mate the coating resistance, R p , which is related to the coating ability to repeal the penetration of the electrolyte and the coat- ing capacitance, C p , which is related to the water uptake [11]. With these parameters it is possible to calculate the remaining coat- ing thickness. Additionally to this electrochemical technique, the easy sample preparation and fast imaging acquisition by environ- mental scanning electron microscopy (ESEM) for non-conductive 0043-1648/$ – see front matter © 2008 Elsevier B.V. All rights reserved. doi:10.1016/j.wear.2008.04.027