Corrosion properties of plasma electrolytic oxidation coated AA7075 treated using an electrolyte containing lanthanum-salts

摘要

Plasma electrolytic oxidation (PEO) is a very promising process that can enhance the corrosion and wear resistance by producing a relatively thick, dense and hard oxide ceramic coating on light alloys. The improvement in the corrosion behaviour of the treated metals strongly depends on some process parameters: current density, voltage, treatment time and electrolyte composition. In particular, the addition of additives in the electrolyte produces significant changes in the corrosion behaviour. The use of rare earth salts, especially of cerium and lanthanum, during PEO treatment was already studied in literature and the use of these salts improved the corrosion resistance of the obtained coatings. However, only few works reported the dissolution of rare earth salts in the electrolyte, whereas in the majority of studies these salts are used in pre-treatment or post-treatment solutions.