Corrosion Behavior Of Bulk Amorphous Alloys In Different Media

Amorphous alloy,also known as metallic glass,is synthesized by modern rapid solidification metallurgy technology.Its internal structure is short-range ordered and long-range disordered,and it has excellent physical and chemical properties of both metal and glass.The corrosion resistance of the alloy is better than that of the crystallized alloy because of its uniform internal structure and lack of internal defects.The study on the corrosion behavior of amorphous alloy is helpful to promote its practical application in engineering.By electric arc furnace smelting of copper and suction casting method was prepared two kinds of glass forming ability good of bulk amorphous alloys（BMGs）Vit1(Zr_41.2 Ti_13.8Cu_12.5 Ni₁₀ Be_22.5)and ZT3(Ti_32.8 Zr_30.2 Cu₉Ni_5.3 Be_22.7).Two kinds of traditional corrosion resistant metal materials,316L stainless steel and TC4 titanium alloy,were selected to compare and analyze the excellent corrosion resistance of amorphous alloy,and the important factors affecting the corrosion resistance were compared and analyzed.In the experiment,HCl,H₂SO₄ and Na Cl were selected as three corrosion media to corrode the materials.Different corrosion methods were adopted for testing.On the one hand,the corrosion rates of the four materials were compared and analyzed by Chemical immersion weightlessness method.On the other hand,the dynamic potential polarization curves and AC impedance spectra of the four materials were tested.The micro-morphology after corrosion was observed by SEM,and the types and contents of the elements after corrosion on the surface were analyzed by EDS.The results show that the corrosion resistance of metal materials is affected by different corrosion methods,different types of corrosion media and the concentration of corrosion media.In the immersion corrosion mode,the amorphous alloy Vit1 and ZT3 are more corrosion resistant than 316L stainless steel and TC4 titanium alloy in the three solutions,and Vit1 has better corrosion resistance than ZT3.After soaking in Na Cl solution for 28d,the amorphous alloy has almost no weight loss and the surface is still smooth and bright.The passive film is intact without obvious damage.Slight pitting corrosion occurs in HCl and H₂SO₄ solution,while 316L and TC4 have obvious weight loss and surface morphology is obviously damaged.Under the electrochemical corrosion mode,the order of corrosion resistance was basically consistent with that of immersion corrosion.The corrosion current density(I_corr)of the amorphous alloy is the smallest,while the transfer resistance(R_ct)is the largest.The main corrosion form is pitting corrosion,and the surface damage degree is smaller than that of 316L and TC4.EDS results show that oxygen elements exist in the corrosion products and exposed surfaces of the four materials.In the solution containing Cl^-,the passive film of the amorphous alloy Vit1,ZT3 and316L stainless steel was eroded and pitting corrosion occurred.The pitting resistance degree was ZT3>Vit1>316L,and the corrosion speed and damage degree of 316L were much higher than that of the amorphous alloy.Although the corrosion rate of TC4 is much higher than that of the amorphous alloy,the passive film is not easily corroded by Cl^-,and the main corrosion mode is uniform and comprehensive corrosion.The corrosion rates of the four metals in sulfuric acid solution are lower than those in hydrochloric acid solution at the same concentration.Among them,Vit1,ZT3 and TC4 maintain stable passivation,and maintain a low current density（I_p）in the passivation state.316L still has obvious pitting corrosion accompanied by uneven overall corrosion.With the increase of medium concentration,the corrosion rate of the four metal materials increases,and the corrosion resistance decreases.In 1 mol/L sulfuric acid solution,the passive film of Vit1 was more corrosion resistant than ZT3,and in 3 mol/L,the passive film of ZT3 with higher titanium content was more corrosion resistant.