Effect of Na 2P 2O 7 electrolyte and al alloy composition on physical and crystallographical properties of peo coating layer : I. physical properties of PEO layer

Abstract

Physical properties of plasma electrolytic oxidized layers of 8 different kinds of Al alloys, A-1100, A-2024, A-5052, A-6061, A-6063, A-7075, ACD-7B and ACD-12 were investigated. The electrolyte for plasma electrolytic oxidation was mixture of distilled water, Na 2P 2O 7, KOH and some metal salts. Growth rate of oxide layer was slower in Na 2P 2O 7 electrolyte system than in Na 2SiO 3 system, and Ra50 surface roughness of oxidized layer was below 1.2 μm. Surface hardness in Na 2P 2O 7 electrolyte system is higher than in Na 2SiO 3 system, and roughness was lower in Na 2P 2O 7 electrolyte system than in Na 2SiO 3 system.