Organic coatings are the principal materials of corrosion protection for all steel structures. In several applications organic coatings have to show, in addition to the anti-corrosion properties, good resistance to impact and abrasion. Thus besides being corrosion resistant, the coatings must be resistant to mechanical damage. Coal tar epoxy coating are widely used in such situations i.e. protecting sea water transferring tubes in which the coatings are subjected to sea water and abrasive particles. In this work the erosion behavior of coal tar epoxy coating has been evaluated by water/sand jet using EIS. During erosion tests water containing sand impacted on the coating and resulted in holes throughout it which led to the diffusion of electrolyte to the coating. The process discussed reduced the protective performance of the coating. After 10 minutes of the erosion test, Nyquist curve showed a semicircle with a large radius and the bode curve showed a capacitance behavior meaning high coating resistance (about 10 9 ?cm 2 ). After 20 and 30 minutes, Nyquist semicircle got smaller and smaller and turned into two semicircles after 45 minutes. In fact, electrolyte penetrated into the coating and led to resistance reduction. At this time, coating resistance was about 500 ?cm 2 having no protective properties. The erosion behavior of the coating was evaluated by mass loss calculation and SEM observation, too. The erosion of the coating was maximal at low impact angles of about 45° displaying a typical ductile character of the coating. However, SEM observation showed craters and cracks formation on the coating at impact angle of 90°. Therefore the coating character is neither typically ductile nor brittle, but a mixture of both. These materials are called ‘semibrittle’. At impact angle of 90°, plastic deformation was observed to be the mechanism of material removal and at oblique impacts erosion occured by the cutting action of the particle. Increasing the particle size and percentage in water resulted in erosion increase due to the higher total enrgy of them. Corrosion behavior of intact coating was evaluated at different temperatures. Increasing corrosion reaction and electrolyte diffusion rates by increasing temperature caused a reduction of the protective performance of the coating. Surface preparation effect on coating adhesion was studied. It showed that samples with surface preparation had a better adhesion to the substrate.