Key factors determining the development of two morphologies of plasma electrolytic coatings on an Al–Cu–Li alloy in aluminate electrolytes

摘要: Abstract The porosity within plasma electrolytic oxidation (PEO) coatings strongly affects their properties, such as the wear resistance. Two typical types of coatings, i.e. bi-layered with large internal pores, which show low resistance, and single-layered excellent performance, have been found following PEO aluminium alloys under pulsed current regimes an aluminate electrolyte. In this paper, mechanisms formation different are investigated discussed based on a thorough investigation Al–Cu–Li alloy using systematic variations 1000 Hz waveforms electrolyte concentration. Both parameters important roles in determining structure resultant coatings. formed dilute electrolyte, containing 5 g l− 1 NaAlO2, were contained both pores pancake structures irrespective application negative pulse. contrast, pulse favored that fewer 32 g l− 1 NaAlO2. A more concentrated 56 g l− 1 resulted relatively compact, independently Similar observations for coating morphologies made if was replaced by high purity also when frequency reduced to 100 Hz. models growth single- proposed.