Comparison of the corrosion behaviour in 5% NaCl solution of Mg alloys NZ30K and AZ91D

Abstract

The corrosion behaviour of AZ91D and NZ30K (Mg-3Nd-0.2Zn-0.4Zr) alloys was investigated in 5% NaCl solution by immersion tests and electrochemical measurements. The immersion tests showed that the corrosion rate of NZ30K was about half that of AZ91D. The localized corrosion of AZ91D was more severe than that of NZ30K due to the higher cathode-to-anode area ratio and higher difference in potential of the cathode phase and the anode matrix. The corrosion of AZ91D concentrated on certain areas and resulted in much deeper corrosion pits, whilst that of NZ30K spread across the surface and led to more uniform and shallow corroded areas. The corrosion products of NZ30K were more compact than those of AZ91D as indicated by SEM. The cyclic polarization curves showed that NZ30K had higher pitting corrosion resistance than AZ91D.

Effect of laser surface melting on corrosion behaviour of AZ91D Mg alloy in simulated-modified body fluid

“…The results suggest that LSM has significant influence on corrosion behaviour of the magnesium alloy due to the refined b-Mg 17 Al 12 phase. In the as-received microstructure, the bulk and lamellar b-Mg 17 Al 12 phase is highly cathodic to the a-Mg phase and can thus act as an effective cathode to cause microgalvanic corrosion [4][5][6][7][8][9]. In the LSM specimens, the original microstructures were refined to the cellular/dendritic structure with the continuous network of fine b-Mg 17 Al 12 phase to provide an effective barrier against corrosion.…”

“…In this alloy, b-Mg 17 Al 12 intermetallic phase normally helps to improve the corrosion resistance [4,5], but the effectiveness of this phase in improving the corrosion resistance depends on its amount and distribution in the a-Mg matrix [6][7][8][9]. A fine and homogeneous b-Mg 17 Al 12 phase provides an effective anticorrosion barrier; however, the presence of coarse and nonhomogeneously distributed b-Mg 17 Al 12 phase could deteriorate the corrosion performance as it can act as a galvanic cathode [6].…”

Influence of Nd and Y additions on the corrosion behaviour of extruded Mg-Zn-Zr alloys

“…However, their poor corrosion resistance in comparison with other metals has greatly retarded further applications. Many intensive and extensive fundamental investigations and evaluations about the corrosion problem of magnesium alloys have been carried out during the past decade [1][2][3][4][5]. However, most of these investigations devoted their research work to the as-cast alloys, such as AZ91D and AM50.…”

Forgeability and die-forging forming of direct chill casting Mg–Nd–Zn–Zr magnesium alloy

“…Elongations of the as-cast, T4 and T6 state NZ30K alloys prepared by permanent mould at RT are 14%, 22% and 11%, respectively [8], which indicates that NZ30K alloy is a potential wrought magnesium alloy. Furthermore the corrosion resistance of as-cast, T4 and T6 alloy is much better than that of AZ91D [9,10]. On the other hand, the NZ30K alloy is cheap for little addition of rare earth.…”