Trans. Nonferrous Met. Soc. China 23(2013) 1002−1010 Cavitation and electrochemical characteristics of thermal spray coating with sealing material Seong-Jong KIM 1 , Seung-Jun LEE 1 , In-Ju KIM 2 , Seong-Kweon KIM 3 , Min-Su HAN 1 , Seok-Ki JANG 1 1. Division of Marine Engineering, Mokpo Maritime University, Haeyangdaehak-ro 91 Mokpo-Si, 530-729, Korea; 2. Korea Institute of Industrial Technology, 89 Yangdaegiro-gil, Ipjang-myeon, Seobuk-gu, Cheonan-Si, 331-822, Korea; 3. Department of Electronic IT Media Engineering, Seoul National University of Science & Technology, 138 Gongneung-gil, Nowon-gu Seoul, 139-743, Korea Received 9 April 2012; accepted 15 August 2012 Abstract: Steel applied in ocean environment is exposed to corrosion and cavitation and is subject to increasing damages. To prevent this, anti-corrosion thermal spray coating technique is widely used. The low-temperature thermal spray coating was performed with 85%Al−14.5%Zn−0.5%Zr for ship materials and various sealing materials were applied to improve its durability, and the electrochemical behavior and cavitation characteristics were observed. The results show that the sealing improves all the properties of the materials. Hybrid ceramic and fluoro-silicon sealing materials show good electrochemical characteristics, and the fluoro-silicon sealing material shows the best anti-cavitation characteristics. Key words: thermal spray coating; sealing material; cavitation; electrochemical characteristics 1 Introduction Since metal corrosion is greatly influenced by flow speed and turbulence flow, that is, when flow speed increases, corrosion is accelerated remarkably [1,2]. Corrosion protection with sacrificial anode clearly decreases life span, and corrosion protection by impressed current tends to increase current density. In the case of sacrificial anode method, design techniques to predict life span are inadequate [3]. If sufficient corrosion protection cannot be achieved, painting must be used, but defective parts of painting exist [4,5]. Thus, corrosion begins from the defective parts and expands to the whole metal due to the defect of coating. As a technique to solve this problem, cold spray coatings which apply corrosion protection coating to metal surfaces were used in various industrial structures. Cold spray coating forms porous metal coating by a process that molten metal is sprayed out from a round slit, the distributed metal droplets hit the steel surface and are laminated and cooled. In the related studies, LIMA et al [6] investigated the fracture toughness and cavitation resistance of thermal spray coating through indentations and found a correlation between the two variables: the higher fracture toughness got, the better cavitation characteristics became. KIM et al [7] studied the void control, abrasion resistance and corrosion resistance of the ceramic spray layer of alumina. In this study, low-temperature spray coating technology with excellent electrochemical characteristics and its cavitation resistance in marine environment was incestigated. Spray coating with 85%Al−14.5%Zn− 0.5%Zr alloy wire for corrosion resistance was applied to steel which was used as a ship material, and the electrochemical and cavitation characteristics of sealing materials were compared. 2 Experimental High tensile steel with composition of 0.1617% C, 0.013% Si, 0.659% Mn, 0.0146% P, 0.0076% S, balance Fe, was used and its tensile strength, yield strength, elongation are 463 MPa, 312 MPa and 23%, respectively. For thermal spray coating, KMS−300 arc spray was used to coat the steel in the thickness of 500 μm or higher with 85%Al−14.5%Zn−0.5%Zr alloy, spray transfer speed of 10 cm/s, gas pressure of 49−58.8 N and wire feed speed of 12 m/min. Thereafter, sealing materials Foundation item: Project supported by the Ministry of Education, Science Technology (MEST) and Korea Industrial Technology Foundation (KOTEF) through the Human Resource Training Project for Regional Innovation Corresponding author: Seung-Jun LEE; E-mail: corr-pro@mmu.ac.kr; Seong-Kweon KIM; E-mail: kim12632@seoultech.ac.kr DOI: 10.1016/S1003-6326(13)62559-5