Investigation of Corrosion and Structural Properties of the Coating Created by Active Screen Plasma Nitriding on Al1050

In this research, the effect of time and temperature of active screen plasma nitriding (ASPN is a novel method of coating) treatment on the surface properties of aluminum alloy 1050 was investigated. Al1050 samples were subjected to ASPN treatment in an atmosphere of %20H2-%80N2 at temperatures of 450oC and 500oC for 5 and 10 hours. The obtained phases and microstructure were studied by Grazing Incidence X-ray Diffraction (GIXRD) and Field Emission-Scanning Electron Microscope (FE-SEM) equipped with EDS analyzer. The corrosion resistance of treated and untreated samples was investigated by polarization and electrochemical impedance spectroscopy (EIS) measurements. The results showed that the formed layer on the surface of specimens consists of Fe2-3N and AlN phases. Microscopic evaluations revealed that the ASPN treatment for 5 hours at 450oC resulted in the formation of nitride grains with an average diameter of ~85nm, while the average size of nitride grains after 10 hours treatment at 500oC was about 233 nm. In addition, as the time and temperature of ASPN treatment increased, the thickness of nitride layer increased from 1.4±0.4 to 5.8±0.9 micrometer. The best corrosion resistance, were measured in the sample of plasma nitrided at 500oC and 10h. The corrosion mechanism of the nitride coating was localized pitting corrosion.