Corrosion of Ni-Al and Ni-Al-Al_2O_3 plasma sprayed coatings in 0.01 M H_2SO_4 and 3.5% NaCl solutions

摘要

In the paper researches results of corrosion properties of Ni-Al alloy and Ni-Al-Al_2O_3 composite coatings were presented. Coatings were obtained by plasma torch. The studies in 0.01 M H_2SO_4 and 3.5 NaCl environments were realized. Measurements were made following methods: polarization and impedance spectroscopy. Rated coatings are more resistant to the 3.5% NaCl environment than the 0.01 M H_2SO_4. Corrosion current density for alloy coatings in artificial seawater was 19 μA/cm~2 and 28 μA/cm~2 environment acidic. Impedance spectroscopy studies showed that the alloy and composite coatings are characterized by greater charge transfer resistance in sodium chloride solution than in sulfuric acid solution. The value of corrosion potential in an environment of 3.5% NaCl is about 300 mV lower than 0.01 M H_2SO_4. Composite coatings Ni-Al-Al_2O_3 were characterized by a higher corrosion current densities and increased resistance than Ni-Al coatings in 0.01 M H_2SO_4 solution. It is related to the porosity of composite coatings. It was found little effect of oxide phase participation on corrosion current density and corrosion potential in 3.5% NaCl environment.