Electrophoretic deposition of polytetrafluoroethylene (PTFE) as anti-corrosion coatings

Abstract

Polytetrafluoroethylene (PTFE) is known as the ‘king of plastics’ because of its excellent resistance for both acid and alkali medium, so the coatings composed of PTFE have an attractive application prospect in the field of corrosion protection. In this work, with a solvent of ethanol containing 0.05 g·L−1 PEI + 0.1 mM nitric acid as the dispersion system, the PTFE coatings were successfully prepared onto the Mg-3Al-1Zn (AZ31) alloy sheets by electrophoretic deposition (EPD) strategy. The morphology of the electrophoretic PTFE coating was further reshaped through a sintering post-treatment at 380 °C in argon atmosphere. In 3.5 wt% NaCl solution, the corrosion current density was remarkably reduced (3.92 × 10−6 A·cm−2 for the bare AZ31 vs 1.54 × 10−9 A·cm−2 for the sintered PTFE coating AZ31), and the charge transfer resistance was significant increased (299.92 Ω·cm2 for the bare AZ31 vs 2.79 × 106 Ω·cm2 for the sintered PTFE coating AZ31), which means the electrophoretic-sintered PTFE coating can significantly improve the corrosion resistance of AZ31 alloys. Moreover, it is also suggested that the electrophoretic-sintered PTFE coating may be a general anti-corrosion strategy for a series of metal materials.