Effect of Current Density on Deposition of Ni-Mn3O4 Composite Coating and its High Temperature Behavior

The combination of electrophoresis and electrodeposition technique is an effective method to increase Mn3O4 particle content in Ni-Mn3O4 composite coatings. The effect of current density during electrodeposition process on the deposition time, surface morphology, and Mn(3)O(4 )content of the composite coating has been systematically studied. Results show that the coatings deposited at a current density of 25 mA cm(-2) for 4.5 min of deposition time are most suitable. Steels with composite coatings deposited under the optimum condition are exposed at 800 degrees C in air for different times to reveal the thermal conversion process. The oxide scale on the samples deposited at 5 mA cm(-2) and 15 mA cm(-2) consists of an external (Ni,Mn,Fe)(3)O-4 spinel layer, a middle NiO layer and an internal Mn-doped Cr2O3 layer after 100 h oxidation. Whereas NiO is non-continuous and embeds in (Ni,Mn,Fe)(3)O-4 /(Ni,Fe)(3)O-4 spinel layer for the samples deposited at 25 mA cm(-2). The scale area specific resistance (ASR) of the sample deposited at 25 mA cm(-2) is lower than those of the samples deposited at 5 mA cm(-2) and 15 mA cm(-2) as well as uncoated steel. (C) 2020 The Electrochemical Society (ECS). Published on behalf of ECS by IOP Publishing Limited.