# Corrosion Assessment of Zr2.5 Nb Alloy in Ringer's Solution by Electrochemical Methods
## 2 Materials and Methods  
The Zr2.5 Nb alloy was purchased from Evek GmbH, Mulheim a.d. Ruhr-Germany in the form of a plate made by cold rolling of zirconium alloys doped with niobium up to 2.5% of the total mass of the material. According to the manufacturer's instructions, this initial alloy was subjected to the vacuum annealing and cold rolled process, providing the following chemical composition shown in Table 1.  
Zr2.5 Nb samples for corrosion tests were prepared in the form of plates with a thickness of 1 mm and dimensions of 25 mm \(\times\) 25 mm, connected to a copper wire (to have electrical contact) after which they were covered with epoxy resin in the form of the film for the subsequent delimitation of the active surface areas of 3.2 cm\({}^{2}\)[12]. The tests were performed at the body temperature of 37 \({}^{\circ}\)C \(\pm\) 0.5 \({}^{\circ}\)C.  
The experimental test protocol, approximately 2 days, was part of the stage of hematoma formation and inflammatory response of a physiological process of bone regeneration, with specific interest in pH variability due to bioactive molecules and other determining factors [10; 11; 13]. The quality of the electrochemical tests was based on the proper processing of the active study surface before immersion in the electrolyte; the samples were cleaned with alcohol, then with hydrochloric acid, rinsed abundantly with distilled water, and finally dried in the oven. To exclude an increased margin of error, the tests were performed 3 times for repeatability, and the experimental data subsequently obtained were processed with accuracy and precision. The Ringer electrolyte was used for electrochemical corrosion because it simulates the internal environment of the human body [14; 15]. Table 2 shows the chemical composition and physical-chemical parameters of the Ringer's solution. The corrosive electrochemical behavior of Zr2.5 Nb alloy was evaluated using a conventional cell with glass walls and pre-drilled organic glass cover to which were attached 3 other electrode support systems, with the aim of sealing the components and the basic \begin{table}
\begin{tabular}{c c c c c c c c c} \hline
**Be** & **Hf** & **Ni** & **Cr** & **Ti** & **Al** & **O** & **Pb** & **Nb** & **Zr** \\ \hline
0.003 & 0.01 & 0.02 & 0.02 & 0.007 & 0.008 & 0.06–0.1 & 0.005 & 2.4–2.7 & Bal. \\ \hline \end{tabular}
\end{table} 
Table 1: Chemical composition of Zr2.5 Nb —wt%. \begin{table}
\begin{tabular}{c c} \hline
**Nr. crt.** & **Chemical Compound** & **Ringer [g/L]** \\ \hline
1 & NaCl & 8.402 \\
2 & KCl & 0.302 \\
3 & CaCl\({}_{2}\) & 0.298 \\
4 & Purified water (H\({}_{2}\)O) & Balance \\ \hline  & pH & 6.79 \\  & Conductivity [mS/cm] & 14.1 \\  & Salinity [ppt] & 8.1 \\ \hline \end{tabular}
\end{table} 
Table 2: Chemical composition and physical-chemical parameters for Ringer’s solution. electrolyte. The electrolyte volume in the electrochemical cell for each experiment was 150 mL. The electrochemical cell used for corrosion investigation was composed by the three electrodes:  
- WE--working electrode, i.e., the studied bio alloy;  
- RE--Ag/AgCl reference electrode (saturated KCl) with a stable potential value of +199 mV compared to the normal hydrogen electrode (NHE);  
- CE--auxiliary electrode or counter electrode--a rectangular grid of Pt (platinum) with an active surface of 4 cm\({}^{2}\)[12]. The electrochemical testing equipment is represented by the electrochemical workstation model PGZ 100 (VoltaLab), but the collection and monitoring of the raw data obtained was performed by a computer whose program runs a suitable software, VoltaMaster4.