Study On Electrochemical Corrosion Behavior And Mechanism Of TZM Alloy In Different Mediums

Titanium-Zirconium-Molybdenum(TZM,0.4% ~ 0.55%Ti,0.06% ~ 0.12%Zr,0.01%~0.04%C)alloy formed by adding a small amount of Ti,Zr and trace elements of C in the Mo matrix.TZM alloy is widely used in the aerospace,power generation,nuclear reactor,military and chemical industries due to their high melting point,high strength,low coefficient of linear expansion and excellent high-temperature properties.Currently,the high temperature oxidation resistance,mechanical properties of the alloy has been studied in detail.However,there are few reports on the corrosion behavior of TZM alloys.Because TZM alloys are widely used in liquid metal-cooled fast neutron proliferators,so it is essential to study the corrosion resistance of the alloy in order to explore whether its scope of application can be further enhanced.TZM alloy and rare earth lanthanum doped La-TZM alloy were fabricated using powder metallurgy and rolling technique.Their electrochemical corrosion behavior was studied quantitatively using potentiodynamic polarization,scanning electron microscope and energy spectrum techniques.In this paper,the electrochemical corrosion behavior of the TZM alloys in different mediums was investigated.Building on previous studies,it is essential to study the electrochemical corrosion resistance and anti-corrosion mechanism of the Pt-coated La-TZM alloy.The results show that Clcorrosion can effectively destroy the passive film formed on the sample surface,pitting and intergranular corrosion of TZM alloy mainly occurr in sodium chloride solution corrosive medium.As the Cl-concentration increases,the corrosion rate of TZM alloy in different Cl-concentrations of corrosive media increases until 1.0 mol/L and then decreases.TZM alloy exhibits good corrosion resistance when the concentration of Clin corrosive media is 0.5 mol/L or 1.5 mol/L.Because of the large accumulation of OHin the area of impurity concentration,irregular surface and narrow slit,the dissolution and cathodic reduction of metal are easy to occur.TZM alloy indicates that the pitting resistance of TZM alloy increases and with growth of OH-concentration,and exhibits the corrosion resistance when the concentration of OH-in corrosive media is 10%.Keeping the Cl-concentrations invariant in neutral,acidic and alkaline medium,the corrosion resistance of the tested TZM alloy is better than that of the La-TZM alloy in neutral and alkaline media,and the alloys are more corrosion-resistant in an acidic medium than in a neutral medium,and are the least corrosion-resistant in an alkaline medium.We found that Cl-effectively destroys the corrosion formed on the surface passivation film,OH-and Cl-double erosion promoted these two types of alloy intergranular corrosion increased,TZM alloy and La-TZM alloy have a good resistance to acidic medium erodibility.Compared with La-TZM alloy,the corrosion current density of Pt-coated La-TZM alloy decreases by 2.14 times and 1.07 times in neutral medium and alkaline medium respectively.The Pt-coated has improved La-TZM alloy corrosion resistance,which may expand the applications of TZM alloys.