# In Vitro Corrosion Behavior of Zn3 Mg0.7Y Biodegradable Alloy in Simulated Body Fluid (SBF)
## 1 Introduction  
Recently, zinc (Zn) and its alloys have attracted considerable attention and are considered promising candidates for various medical applications, due to the much more suitable degradation rate compared to magnesium (Mg) and iron (Fe) alloys. However, it is important to note that its mechanical properties need to be improved to meet the standards for medical applications. The yield strength (MPa) of Zn-based alloys presents many variations based on their added elements and states (cast, heat treated, laminated, severe plastic deformation or powder metallurgy and additive manufacturing). The values obtained experimentally vary from 50 to 500 MPa from ZnCu to ZnCuMg or ZnLi alloys, respectively [1, 2]. Vickers hardness (HV) was also reported with different values from 30 to 150 HV [1]. [PERSON] et al. [3] studied the behavior of a complex Zn alloy (96.5% Zn) in marking out a uniform corrosion and a homogenous distribution of various reaction products obtained during the long-term immersion in SBF. Additionally, [PERSON] et al. [4] studied a few Zn-Fe-Mg alloys in SBF and found that the Zn1 Fe1 Mg shows a good corrosion rate and superior mechanical properties. The corrosion rate of Zn-based alloys is influenced by the alloyingelements and ranges from almost 0.050 mm/year to more than 0.300 mm/year determined by a potentiodynamic polarization test in [PERSON]'s electrolyte solution [1]. Electro-corrosion determinations show that the values of corrosion potential and the corrosion current density of zinc and Zn-based alloys are between those of magnesium- and iron-based alloys [5]. The corrosion compounds from the surface are generally made of oxides, hydroxides and phosphates of the main elements. After years of developing strategies and methods to improve or even combat the corrosion of metallic biomaterials, there is now a growing interest in the use of corrodible metals in medical device applications. These are called biodegradable or absorbable metals [6], as they are expected to gradually corrode in vivo by generating an appropriate host response and then dissolve completely upon tissue healing [7]. A gradual transfer of the load to the healing tissue and the prevention of secondary surgery are the two main reasons why this category of metals are favorable alternatives to existing corrosion-resistant metal implants used for temporary applications [8]. Metallic materials have been investigated mainly for absorbable medical devices [9]. Zinc and zinc-based alloys are very active metals in ionic media, especially in the presence of chlorine ions. In the last decade, in the field of biodegradable metals used to make implants that after a certain time must be removed from the body, more and more attention has been paid to zinc and zinc-based alloys [10; 11; 12]. The advantages of using these materials can be summed up by the fact that they have an average corrosion rate between the corrosion rates of magnesium and the corrosion rate of iron (standard electrode potential: Mg (\(-\)2.61 V) \(<\)Zn (\(-\)1.008 V) \(<\)Fe (\(-\)0.685 V vs. ENH) [13]. Additionally, zinc is an essential element from a biological perspective [14], having an excellent hemocompatibility, and its corrosion products work as an anti-inflammatory. Zinc has an electrode potential between those of magnesium and iron, satisfying clinical requirements, and being a good candidate as a biodegradable metal [15; 16]. Moreover, zinc is widely recognized as a nutrient with an important biological function involved in synthesis, such as DNA polymerase, RNA polymerase and many transcription factors [17]. Zn was further investigated for potential clinical applications [18]. Due to the low mechanical strength and low hardness, like Mg, Zn may not meet the requirements for the mechanical properties of the implant materials. To improve their mechanical performance, a good technique is alloying with different elements. Such Zn alloys are Zn-Mg alloys [19; 20], or in our case, we propose ZnMgY alloys.