AZ91 alloy

Fig. 14. Effects of iron (—), nickel (-), and copper (...) contaminant levels on the saltwater corrosion performance of magnesium AZ91 alloy containing...

K. N. Reichek, K. J. Clark, and J. E. HiUis, Controlling the Salt Water Corrosion Peformance of Magnesium AZ91 Alloy, paper 850417, Society of Automotive Engineers, Detroit, Mich., 1985. 

Corrosion rates of 0.1-0.2 mg/cm /day under ASTMB117 salt fog conditions are typical for WE54 and the high purity AZ91 alloys which are comparable with those of some aluminium alloys. This considerable... 

Reichek, Clark, Hillis, Controlling the Soli Water Corrosion Performance of Magnesium AZ91 Alloy, SAE Paper 850417... 

The effect of heat treatment is to alter the size, amount and the distribution of the precipitated /(-phase, Mg17Al12, which in turn affects the corrosion rates of AZ91 alloys, as shown in Table 4.72. 

Example 17.1 Plots for Mg Alloys Consider the global impedance response for an as-cast magnesium alloy AZ91 presented in Figure 17.11 for the AZ91 alloy at the corrosion potential after different immersion times in 0.1 M NaCl. What quantitative information can be obtained without considering a detailed process model such as discussed in Example 10.3 ... 

T.R. Thomaz, C.R. Weber, T. Pelegrini, L.F.P. Dick, G. Knomschild, The negative difference effect of magnesium and of the AZ91 alloy in chloride and stannate-containing solutions, Corros. Sci. 52 (2010) 2235-2243. 

Shkurankov A, El Abedin SZ, Endres F (2007) AFM-assisted investigation of the corrosion behaviour of magnesium and AZ91 alloys in an ionic liquid with varying water content. Aust J Chem 60(1) 35 2. doi 10.1071/ch06305... 

FIG. 2—Effect of iron, nickel, and copper contaminant levels on ASTM B 117 salt spray corrosion rates In AZ91 alloy versus cold-rolled steel and 380 die cast aluminum [10,19]. 

FIG. 3—Relative weight loss associated with dissimilar metal fasteners in AZ91 alloy exposed to ASTM salt spray [51,52]. 

Hallopeau X., Beldjoudi T., Fiaud C., Robbiola L. (1997), Electrochemical behaviour and surface characterisation of Mg and AZ91E alloy in aqueous electrolyte solutions containing XOyn- inhibiting ions , in G.W. Lorimer (ed.). Proceedings of the Third International Mg Conference, The Institute of Materials, London, pp. 713-724. 

Influence of RE element on passivity behavior of AZ91 alloy... 

In this section, the wrought AZ91 alloy was fabricated as follows the cast ingots were extruded at 230-240 °C with a horizontal water press, the rate was 2-3m/min and the extrusion ratio was 18 1. 

The potentiodynamic anodic polarization plots of wrought AZ91 alloy without and with Ce in 0.01 M NaOH aqueous solution are shown in Fig. 4.21. It can be seen that the anodic polarization plot of wrought AZ91 alloy without Ce shows an active-passive behavior. A decrease in current density at potential above -1.456Vsce is observed. Within the potential range of passivity, a relative small passive current density (about 4 x 10" A/cm ) is observed, which is potential-dependent. 

The polarization plot of wrought AZ91 alloy with Ce differs from that of wrought AZ91 alloy without Ce. For wrought AZ91 alloy with Ce, the... 

The potentiodynamic anodic polarization plots of wrought AZ91 alloy without and with Ce in 0.01 M NaOH. 

Mott-Schottky (M-S) plots of passive films on wrought AZ91 alloys without and with Ce are shown in Fig. 4.26(a). As it can be seen, the positive slopes are obtained on wrought AZ91 alloy without and with Ce, which indicate n-type semiconductors of passive films for two alloys. Namely, Ce in wrought AZ91 alloy does not change the type of semiconductor. 

The slope of 1/C versus V plot is inversely proportional to carrier concentration (donor or accepted). The slope of wrought AZ91 alloy without... 

M-S plots of the passive films for wrought AZ91 alloy without and with Ce (a), sketch presentation of the electronic structure of n-type passive film at anodic potential (b). 

The results of the potentiostatic polarization and EIS have showed that the passive film formation processes for two alloys are diffusion-controlled processes, which means the diffusion stage is slower than the electrochemical stage during the passive film formation process. The metal ionization process at the interface of metal and film was the electrochemical process. The process was more rapid than the diffusion process, which led to metal ions or oxygen vacancies predominated in the passive film. This kind of passive film has an n-type semiconductor character. Therefore, the passive films of wrought AZ91 alloy without and with Ce addition present n-type semiconductors. 

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