Certain characteristics of composite polytetrafluoroethylene-oxide coatings on aluminum alloy

We present the results of an investigation of the distribution of of elements according to cross-section morphology, adhesion, and anticorrosive properties of PTFE-oxide layers formed by plasma-electrolytic oxidation in an Na2SiO3 + NaOH electrolyte with dispersive particles of PTFE stabilized by siloxane acrylate emulsion. Coatings have a structure uncharacteristic of PEO layers. The main coating mass of thickness of up to 80 μm is composed of polytetrafluoroethylene and decomposition products of PTFE particles, as well as of the emulsion. The transition layer between the metal and polymer coating has a thickness of ∼10 μm and contains oxides of aluminum and silicon. Sample weight loss after ultrasonic treatment in water is ∼1%, which indicates a satisfactory adhesion of the coating to the metal and the cohesion between coating fragments. The coatings have a complex surface with pores several tens of microns in size. After annealing in air at 200°C, pores are filled with polymer, which is accompanied by a significant improvement in the coating’s anticorrosive properties. As a result of annealing in air at 400°C, the polymer coating sublimates and the transition layer with a thickness of ∼10–15 μm remains.