Investigation the effect of conducting electrolyte on the characteristics of nano-structure aluminium oxide coatings produced via plasma electrolyte oxidation

Plasma electrolytic oxidation (PEO) is a plasma-assisted electrochemical process which can improve the tribological properties of light alloys. Unlike the anodizing process in which acidic electrolytes are used, alkali electrolytes are utilized in these processes. For increasing the electrical conductivity of the electrolyte, some salts are added to the electrolyte. A high frequency pulsed DC plasma electrolytic oxidation was utilized to treat the surface of aluminium in low concentrated alkali electrolyte. The electrolytes consisted of potassium hydroxide in two separate solutions; one mixed sodium silicate and the other in combination with sodium aluminate. Scanning electron microscopy, X-ray diffraction analysis and Vickers micro-hardness tests were used to characterize the coatings. The results showed that the coatings had nano-crystalline structure. Silicate electrolyte results in higher porosity and roughness and lower hardness if compared to those of coatings produced in aluminate electrolyte.

کلیدواژه ها:

plasma electrolytic oxidation ، aluminium oxide ، silicate solution ، aluminate solution