Electrophoretic Deposition of Ni Nano-Particles for Self-Repairing of Heat Exchanger Tubes

Abstract

The electrophoretic deposition process of Ni nano-particles in organic suspension was employed for self-repairing of heat exchanger tubes. For this purpose, Ni nano-particles prepared by levitation-gas condensation were dispersed into the solution of ethanol with the addition of dispersant. The pitted Ni alloy specimen was prepared by applying a potential of 0.9 V (vs. Ag/AgCl) in aqueous 0.1 M NaCl solution. For electrophoretic deposition of Ni nano-particles on the specimen, a constant electric field of 100 V cm-1 was applied to the specimen for 180 s in Nidispersed solution. It was found that as the electrophoretic deposition time increased, the size of the pit remarkably decreased due to the agglomeration of Ni nano-particles at the pit with a higher current value rather than the outer surfaces of the specimen with a lower current value. Moreover, the current density increased with electrophoretic deposition time and reached a constant value. From the above, it is concluded that as the electrophoretic deposition proceeds, the pit becomes smaller in size, and hence the nano-particles more extensively aggregate at the pit by lyosphere distortion.