Properties of Zinc Alloys

Engineering Properties of Zinc Alloys, International Lead Ziuc Research Organization, New York, 1980, pp. 1—36. 

Table 4.39 Typical Mechanical Properties of Zinc Alloys...

Chandrasekar MS, Srinivasan S, Pushpavanam M (2008) Properties of zinc alloy electrodeposits produced from acid and alkaline electrolytes. J Solid State Electrochem 13 781-789. doi 10.1007/sl0008-008-0607-2... 

Table 6-2 Composition (wt.%) and properties of zinc alloys for anodes...

Magnesium anodes usually consist of alloys with additions of Al, Zn and Mn. The content of Ni, Fe and Cu must be kept very low because they favor selfcorrosion. Ni contents of >0.001% impair properties and should not be exceeded. The influence of Cu is not clear. Cu certainly increases self-corrosion but amounts up to 0.05% are not detrimental if the Mn content is over 0.3%. Amounts of Fe up to about 0.01% do not influence self-corrosion if the Mn content is above 0.3%. With additions of Mn, Fe is precipitated from the melt which on solidification is rendered harmless by the formation of Fe crystals with a coating of manganese. The addition of zinc renders the corrosive attack uniform. In addition, the sensitivity to other impurities is depressed. The most important magnesium alloy for galvanic anodes is AZ63, which corresponds to the claims in Ref. 22. Alloys AZ31 and M2 are still used. The most important properties of these alloys are... 

This example of aluminium illustrates the importance of the protective him, and hlms that are hard, dense and adherent will provide better protection than those that are loosely adherent or that are brittle and therefore crack and spall when the metal is subjected to stress. The ability of the metal to reform a protective him is highly important and metals like titanium and tantalum that are readily passivated are more resistant to erosion-corrosion than copper, brass, lead and some of the stainless steels. There is some evidence that the hardness of a metal is a signihcant factor in resistance to erosion-corrosion, but since alloying to increase hardness will also affect the chemical properties of the alloy it is difficult to separate these two factors. Thus althou copper is highly susceptible to impingement attack its resistance increases with increase in zinc content, with a corresponding increase in hardness. However, the increase in resistance to attack is due to the formation of a more protective him rather than to an increase in hardness. 

The physical properties of zinc and the diecasting alloys are given in Table 4.31. 

Table 4.31 Physical properties of zinc and cast zinc alloys...

The corrosion reactions may be slowed down by using zinc alloys (with lead and cadmium, also improving the mechanical properties of zinc to simplify the production process) instead of the pure metal, or by amalgamating the inner surface of the can by adding a small amount of a mercury compound to the electrolyte. 

Refs. [i] Habashi F (ed) (1998) Alloys, preparation, properties, applications. Wiley-VCH, Weinheim [ii] Matucha KH (1996) Structure and properties of nonferrous alloys. In Matucha KH (ed) Materials science and technology. A comprehensive treatment, vol 8. VCH, Weinheim [iii] Fleischer A, Lander J, (eds) (1971) Zinc-silver oxide batteries. Wiley, Chichester [iv] Hicks HG (1960) The radiochemistry of zinc. McGraw-Hill, New York [v] Linden D, Thomas BR (eds) (2002) Handbook of batteries, 3rd edn McGraw-Hill, New York [vi] Pauling L (1970) General chemistry, 3rd edn. Freeman, San Francisco [vii] Lide DR (ed) (2003-2004) Handbook of chemistry and physics, 84th edn. CRC Press, Boca Raton [viii] http //periodic.lanl.gov/elements/30.html... 

While not investigated in depth, the un-reacted ash can be subjected to a mixture of hydrogen and oxygen, with sufficient oxygen to raise the temperature above the melting point of the steel. This will melt the ceramic materials to an ash and allow the recovery of the metals as a peculiar mixture of iron, nickel, chromium, lead, tin, copper, zinc and other metals. The properties of this alloy are not known, but it may be useful in applications where a metal is desired but high quality is not essential. It may also be possible to reprocess this alloy to recover the pure metals. 

B. Properties of other Alloys, given for Reference in a Supplementary Section (1) Alloys of Aluminium and Zinc. 

The external layer of pure zinc is of primary importance with regard to the corrosion resistance of the bars. If galvanized steel is exposed to a neutral environment, such as the atmosphere, the duration of protection is primarily dependent on the thickness of the zinc coating, and its composition and microstructure has a negligible effect. Similarly, for galvanized-steel bars embedded in concrete, the protective properties of zinc coatings are due for the most part to the external layer of pure zinc, which can form a passive film if it has a sufficient thickness [36-39]. In fact, a loss of thickness of 5-10 pm is required prior to passivation, while, if the thickness is insufficient, the underlying layers of Zn-Fe alloy passivate with more difficulty. 

Magnesium and zinc are the predominantly used galvanic anodes for the cathodic protection of pipelines [13—16]. The corrosion potential difference of magnesium with respect to steel is 1 V, which Umits the length of the pipeline that can be protected by one anode. Economic considerations have led to the use of aluminum and its alloys as anodes. However, aluminum passivates easily, decreasing current output. To avoid passivation, aluminum is alloyed with tin, indium, mercury, or gallium. The electrochemical properties of these alloys, such as theoretical and actual output, consumption rate, efficiency, and open circuit (corrosion) potential, are given in Table 15.1. 

Zinc in alloyed form can be cast with fine detail into complicated shapes and can be formed with extra thin walls (0.5 mm). Specifiers can choose from a family of zinc alloys and a range of casting processes that are the most suited for their products. Zinc alloy castings are unique, particularly when produced by the pressure die-casting process. They can be made to extremely close tolerance, with excellent surface finish, have a range of useful physical and mechanical properties and can receive a wide range of applied finishes. Typical applications are precision parts for vehicles, aircraft and communications equipment, plumbing hardware, construction fixtures, household appliance, zippers and toys. 

Petrov, L. (1968). Effect of the etching of zinc alloys in nitric acid on their strength properties. Fiz. Khim. Mekh. Mater., 4(6), Til (in Russian). 

Tano, K., and Higuchi, S. (1985). Developnaent and properties of zinc-aluminum alloy coated sheet with high corrosion resistance. Nippon Steel Technical Report 25, pp. 29-37. 

Industrially, the most important property of zinc metal is its ability to form an alloy with iron so that a thin adherent layer can be applied to the surface of iron workpieces. The zinc coating, obtained either by hot-dip galvanizing or aqueous electrogalvanizing, considerably extends the service life of steel constructions. In addition, zinc alloys can be easily cast into intricate shapes that are used extensively in household goods and automotive equipment, building, and construction utilities. Other important areas are brasses, batteries, tires, and other rubber goods. Furthermore, zinc is now known to be an essential nutrient that is indispensable for human health as well as for many species of animals and plants, and it is therefore used in pharmaceuticals, fertilizers, and animal feed. 

Ares, A.E. Gatti, I. P. Gueijman, S.F. Schvezov, C.E. (2009) Mechanical Properties of Zinc-Aluminum Alloys versus Structural and Thermal Parameters, Proceedings of MCWASP International Conference Modeling of Casting, Welding and Advance Solidification Processes - XII, Vancouver, Canada, June of 2009... 

Zinc used as a sacrificial material should be characterized by high purity (99.99% Zn, less than 0.003% Fe). The presence of impurities such as iron, copper, and lead very negatively affects the work of a sacrificial anode. They cause passivation of the surface of zinc as a result of which the polarization current decreases in the protection system and the current output is decreased. In order to improve the sacrificial properties of zinc, small amounts of alloy additives are introduced. The following have an advantageous effect aluminum (0.1-0.5% Al) and cadmium (0.02-0.15% Cd), and aluminum (0.5% Al) and silicon (0.1% Si). 

The mechanical properties of zinc casting alloys are shown in Table 23.6. 

---