3-Dimensional structures of open-pores in PEO films on AZ31 Mg alloy

Abstract

In this work, observation of 3-dimensional network structure of open-pores in plasma electrolytic oxidation (PEO) films is reported for the first time using a resin replica method. Conventional plane and cross-sectional views of PEO films provide only 2-dimensional information on the shape and size of pores in PEO films, while an epoxy replica, which was prepared by infiltrating a mixture of liquid epoxy resin and hardener into the open-pores in PEO films under high vacuum and hardening at room temperature, rendered clearly 3-dimensional information about the shape, size and position of open-pores in PEO films. The resin replica method, applied to PEO films on AZ31 Mg alloy formed in phosphate solution, revealed not only 3-dimensional network structures of irregular shape of large size and small size pores, in the middle part and near the film/alloy interface, respectively, but also spherical pores connected to the surface through narrow channels.