The Corrosion Behaviors Of Al-Zr-Nd And Al-Fe-Zr-Nd Alloys

The Al-(Fe)-Zr-Nd alloys were prepared by arc melting and annealed up to one month at500℃. The phases composition of alloys, as well as polarization cures, surface morphology before and after immersion in acid, alkali and saline solutions, and after electrochemical polarization were investigated by X-ray diffraction, metallurgical microscope and electrochemical workstation. The results showed that:(1) The Al-Zr-Nd alloys were located in four different equilibrium phase regions, and Al10Fe2Nd compound was found in part of alloys after the addition of Fe. The texture structures of alloys were coarse when the content of Al up to85at.%and were refined with increasing the content of Nd.(2) In3.5%NaCl solution, pitting corrosion occurred in the alloys which are mainly composed of Al solid solution and expanded to Al substrate, resulting in selective corrosion. For the other alloys, pitting corrosion was not observed, the selective corrosion existed at defect and grain boundary and then the easy corrosion phases. Passivation was only observed in anode polarization of the alloys which are mainly composed of Al solid solution. The corrosion phenomena became more serious but pitting corrosion was not observed after the addition of Fe. Al solid solution was priority dissolution and then the ternary compound Al10Fe2Nd due to galvanic corrosion, the corrosion resistance of the binary phases composed of Al and Zr were the highest.(3) In0.1M H2SO4solution, pitting corrosion was not observed in all alloys. The corrosion began from defect and grain boundary, and then expanded to the easy corrosion phases in some alloys. The corrosion phenomena became more serious with decreasing the content of Al in the alloys. The corrosion resistance was improved due to the exist of Al10Fe2Nd phase after the addition of Fe, but in reverse without the Al10Fe2Nd.(4) In0.1M NaOH solution, the alloys which are mainly composed of Al solid solution were corroded seriously and the Al substrate was dissolved due to galvanic corrosion, the corrosion current density of them up to the magnitude of mA/cm2but the others were very small. The corrosion existed at grain boundary or the easy corrosion phases and became more serious for all the alloys after the addition of Fe.