Molten Salt Electrodeposition of Ni Aluminide Surface Layer and High Temperature Oxidation Resistance

Abstract

A Ni aluminide layer on Ni substrate was formed by electrodepositing Al and alloying it with Ni in molten salt. Electrolysis of Al was conducted using potentiostatic polarization method at constant potentials in an equimolar NaCl-KCl melt containing 1∼5 mol%AlF₃ at 1023 K. The mass of electrodeposited material increased with an increase in polarization potential. Deposits formed at −1.2∼−1.4 V(vs. Ag/Ag⁺(0.1)) built up a homogeneous layer. These deposits consisted of Ni aluminide such as Ni₂Al₃ and NiAl. Al content in deposit layers slightly decreased with increasing depth from the surface to the deposit/substrate interface. Nickel covered by the electrodeposit layer was more resistant than bare nickel to high temperature oxidation.