CHARACTERIZATION AND CATHODE ELECTROPHO-RESIS DEPOSITION OF CERIUM MODIFIED FILMS ON Al 5083

The effect of Cu content on the corrosion resistance of Zr-1%Nb-xCu(x=0.05%- 0.5%,mass fraction) was investigated in superheated steam at 500℃and 10.3 MPa by autoclave tests.The microstructures of the alloys and oxide films on the corroded specimens were observed by TEM and SEM,respectively.The results showed that when the Cu content was below 0.2%, the corrosion resistance of the alloys was markedly improved with the increase of Cu content,while further addition of Cu did not lead to a further improvement in the corrosion resistance.When the Cu content was below 0.2%,the Cu mainly dissolved in theα-Zr matrix.And when the Cu content was more than 0.2%,part of Cu precipitated as Zr_2Cu second phase particles.When theα-Zr matrix was oxidized,the Cu dissolved in theα-Zr could delay the process that the vacancies in the oxide film diffused and coalesced to form pores,and the pores developed into micro-cracks. Therefore,the corrosion resistance of the alloys was enhanced.It can be concluded that the Cu concentration in theα-Zr matrix,rather than the second phase particles containing Cu,is the main reason that the addition of Cu improves the corrosion resistance of M5 alloy in superheated steam at 500℃and 10.3 MPa.