23. - 25. 5. 2012, Brno, Czech Republic, EU ZN-BASED ALLOYS AS AN ALTERNATIVE BIODEGRADABLE MATERIALS Jiří KUBÁSEK, Dalibor VOJTĚCH Department of Metals and Corrosion Engineering, Institute of Chemical Technology, Prague, Technicka 5, 166 28 Prague, Kubasekj@vscht.cz Abstract Zinc like magnesium has important role in many biological processes in human organism. However, recommended dietary allowance (RDA) for zinc is 15-40 mg per day which is much lower in comparison with 300-400 mg for magnesium. For this reason biodegradable materials based on Zn should be characterized by lower corrosion rate in comparison with magnesium materials. Sufficient mechanical properties especially high strength and medium ductility are required. Poor mechanical properties of pure zinc can be increased by alloying with other elements. In this research magnesium was used as alloying element due to its beneficial effect on bone growth. Binary zinc alloys that contained from 0.5 to 3 wt. % of magnesium were prepared. Mechanical properties of studied alloys in the cast state were determined and compared to pure Mg and Zn. Moreover, corrosion behaviour in physiological NaCl solution and simulated body fluid (SBF) solution was studied by immersion tests and potentiodynamic measurements. Maximum strength of 150 MPa was achieved in the case of Zn-1Mg (wt. %) binary alloy. Corrosion rates of Zn-Mg alloys were determined to be significantly lower than that of pure Mg. Both mechanical and corrosion properties are discussed in relation to the structural features of the alloys. Key words: zinc alloys, biodegradability, corrosion, mechanical properties 1. INTRODUCTION Biodegradable materials can be gradually dissolved and absorbed in organism [1, 2, 3]. In this group polymeric, ceramic and metal materials are included. In comparison with polymeric and ceramic ones metallic biomaterials are characterized by higher strength and fracture toughness [4] which mean that they are more suitable for load-bearing applications [5]. Currently, biodegradable metallic materials are based on magnesium. Magnesium is not toxic even in quite high daily doses. His recommended dietary allowance (RDA) for adults is 300 – 400 mg per day [6]. Magnesium itself support some biological processes such as functions of muscles, nerves, heart and has positive influence on the growth of bones [1, 2, 7, 8]. Moreover Young´s modulus of magnesium is close to human bones, which is important to prevent stress -shielding effect [1, 2]. On the other hand pure magnesium is often characterized by high corrosion rate in body fluids. Excessive corrosion rate can lead to formation of hydrogen pockets and disruption of some pH dependant physiological reaction balances [2]. Uniform corrosion, acceptable corrosion rate and improved mechanical properties are main requirements for new biodegradable materials. For this reason different magnesium alloys with rare earth elements, aluminium, zinc, calcium, manganese have been tested recently [9 - 14]. It is considered that suitable alloying with rare earths elements can slow down corrosion process of magnesium alloys, however there is still lack of information about toxicity of members of this group [2, 15, 16]. Other element such as aluminium is still associated in connection with Alzheimer´s disease [9]. Different alloys with zinc as a main constituent were prepared [9 - 14]. It is known that zinc can positively affect the corrosion rate and mechanical properties of magnesium alloys [9]. Moreover it is important element for functions of enzymes, immune functions, wound healing, it supports normal growth and proper sense of taste and smell [9, 15, 16]. Magnesium alloys in the form of metal glasses that contained about 50 wt.% of zinc with excellent