Estudo de corrosão de revestimento ferro/níquel/cromo em substrato de aço Domex 700

Abstract

DOMEX 700 steel was developed to replace the usual carbon steels, being known as high strength steel and low alloy, due to the small percentage of alloying elements in its composition, besides high resistance when compared to carbon steels, being characterized by ferrite fines grains. In this work, an iron / nickel / chromium coating was deposited using plasma magnetron sputtering, aiming to study the coating effects on the corrosion rate. For the analysis, electrochemical techniques were used in an aerated solution of NaCl (3.5%), at room temperature, including measurement of open circuit potential, micropolarization and macropolarization. With the experimental data, the corrosion rate in mm / year of both the base metal and the coating were calculated. In addition, metallographic analyzes of the steel microstructure were performed using optical microscopy and the chemical composition was determined by X-ray fluorescence. The obtained corrosion results indicate that the base metal has a corrosion rate of 0.01 mm / year while the material with the coating had a corrosion rate of 0.05 mm / year. The reduction in the corrosion rate was associated with the formation of a non-homogeneous coating, with flawed coating growth, which generated sharp corrosion in the exposed interstices of the base metal, since the graphical polarization analysis indicates that the nature of the oxy-reduction reactions was maintained.