Influence of adding glass beads in cathode region on the kinetics of cathode plasma electrolytic depositing ZrO2 coating

• Glass beads were added in cathode region in CPED process to prepare ZrO2 coating.
• Cathode current density–voltage curves (jc–V curves) were measured.
• Kinetics of CPED ZrO2 coating with and without glass beads was investigated.
• Plasma discharge ignition current density is reduced by 2 orders of magnitude.
• Uniform ZrO2 coating can be deposited on the cathode surface with large area.

The ZrO2 coating was prepared by cathode plasma electrolytic deposition (CPED), the cathode current density–voltage curves were used to investigate the influence of adding glass beads in the cathode region on the kinetics of the CPED process. With adding glass beads in the cathode region, the cathode current density for plasma discharge ignition is reduced by 2 orders of magnitude, plasma discharges take place randomly on the whole cathode surface. Consequently, a uniform ZrO2 coating can be deposited on the cathode with a large area. These beneficial effects can be attributed to the fact that the transportation of gas bubbles in the solution near the cathode surface is inhibited and electric field distribution becomes more uniform in the presence of glass beads in the cathode region. Therefore, a thin and uniform bubble sheath is formed at a low cathode current density, and a high electric field strength is established to ionize this bubble sheath. This work is expected to promote the development of CPED technique towards deposition of various ceramic coatings on large samples.