The corrosion resistances of both CNTs reinforced and non-CNTs reinforced Al2O3 coatings were investigated by using different such techniques as: potentiodynamic polarization; electrochemical impedance spectroscopy (EIS); salt spray and erosion corrosion tests. The obtained results show positive effects of CNT to improve the corrosion protection of the Al2O3 coating: time of appearance of first rust points on the surface in the salt spray test increased from 2 hours for pure Al2O3 coating to 24 hours for the CNTs-Al2O3 one; the erosioncorrosion resistance of the CNTs-Al2O3 coating increased about 17 % in comparison with the one of the Al2O3 coating. | Vietnam Journal of Science and Technology 55 (5B) (2017) 171-180 STUDY ON CORROSION RESISTANCE OF CARBON NANOTUBES REINFORCED Al2O3 COATING Nguyen Van Tuan1, *, Ly Quoc Cuong1, Le Thu Quy2, Pham Thi Ha1, Pham Thi Ly1 1 Institute for Tropical Technology, VAST, 18, Hoang Quoc Viet, Cau Giay, Ha Noi, Viet Nam 2 National Key Laboratory for Welding and Surface Treatment Technologies, NARIME, 4 Pham Van Dong, Cau Giay, Ha Noi, Viet Nam * Email: nvtuan@ Received: 11 August 2017; Accepted for publication: 7 October 2017 ABSTRACT This paper presents our research on the reinforcement with 1 % of carbon nanotubes (CNT) for a ceramic Al2O3 coating applied by air plasma spray (APS) on CT3 steel. The corrosion resistances of both CNTs reinforced and non-CNTs reinforced Al2O3 coatings were investigated by using different such techniques as: potentiodynamic polarization; electrochemical impedance spectroscopy (EIS); salt spray and erosion corrosion tests. The obtained results show positive effects of CNT to improve the corrosion protection of the Al2O3 coating: time of appearance of first rust points on the surface in the salt spray test increased from 2 hours for pure Al2O3 coating to 24 hours for the CNTs-Al2O3 one; the erosioncorrosion resistance of the CNTs-Al2O3 coating increased about 17 % in comparison with the one of the Al2O3 coating. Keywords: Al2O3 coating; air plasma spray; carbon nanotubes 1. INTRODUCTION Plasma spray is one of the thermal spray methods that are commonly used to create coatings with advanced surface properties. The technique can create a variety of coatings such as metal coatings, ceramic coatings and metallic ceramic coatings [1]. Plasma coatings are mainly used in erosive, corrosive and high temperature environments [2 - 5]. Al2O3 coating was prepared by the plasma spray technique with heterogeneous structure. Inside the coating, there are always defects, cracks and micropores which affect the working capability of the coating [6 - .