Effect of ytterbium on the microstructure and efficiency of Al-Zn anodes in different chloride concentrations by...

In modern industrial applications, metal structures will be exposed to severe corrosive environments, leading to reduced service life and performance. The use of sacrificial anodes for cathodic protection remains one of the most effective mitigation or prevention methods, where aluminum-based alloys are widely used due to their high current capacity and cost efficiency. This study investigated the effect of the addition of ytterbium (Yb) on the microstructure and electrochemical performance of an Al-Zn sacrificial anode in various aqueous media. Alloys containing 0, 1, 2, and 3 wt% Yb were fabricated and characterized using OES-AAS, XRD, SEM-EDX, metallography, and potentiostat testing, while the efficiency of the anode was evaluated according to the DNVGL-RP-B401 standard. The results showed that Yb acts as a grain refiner, which promotes the formation of the intermetallic compound YbZn₂ along the grain boundaries, resulting in a smoother and more uniform microstructure. The corrosion rate of samples containing 0, 1, 2, and 3 wt% of Yb was 0.38348, 0.12049, 0.10367, and 0.059231 mm per year based on measurements of potentiodynamic polarization in 3.5 wt% NaCl electrolytes. A decrease in the corrosion rate is experienced as the increased content of Yb is incorporated into the formation of a more uniform grain structure, which forms a more homogeneous anodic dissolution. Based on the anode efficiency test carried out according to the DNVGL-RP-B401 standard, the efficiency of the sacrificial anode increased with the content of Yb. In a solution of 3 wt%, the anode efficiency of alloys containing 0, 1, 2, and 3 wt% Yb is 59.35%, 81.46%, 89.14%, and 94.74%, respectively. In contrast, testing in a 3.5 wt% NaCl solution resulted in lower anode efficiency: 54.70%, 74.80%, 85.45%, and 91.44%, respectively. These findings illustrate that Yb microalloys effectively improve the performance and anode capabilities of sacrificial aluminum in chloride-rich environments.