Marine vessels have numerous metallic components such as propellers, rudderstocks and general fittings. Under normal circumstances, these elements in the boat would become degraded quickly because of their contact with saline water. However, this problem can be resolved through the installation of a sacrificial or galvanic anode. The anode is a reactive rod fitted into the boat and corroded in place of the metallic elements in the vessel.
If you are planning on installing a new sacrificial anode in your marine vessel, you must choose between aluminium and zinc products. Both options are beneficial for cathodic protection applications in boats. Numerous sailors prefer to use zinc elements because they are well-known. However, aluminium anodes have some distinct advantages over this alternative. Here are the reasons you should consider choosing aluminium galvanic rods over zinc in oceanic environments.
Level of Protection
When looking for sacrificial anodes for your applications, you should think about the level of protection provided by the different products. In general, aluminium is more favourable than zinc for marine applications because the electrical potential to absorb corrosion is high. This metal will protect the boat in both salt and brackish water, promoting the optimal longevity of components. On the other hand, zinc has a considerably low driving voltage. The material will provide excellent protection in salt water. However, if the water is not adequately saline, there will be insufficient current for complete coverage because of the low voltage.
Sacrificial anodes can become passive in particular environments. When this process occurs in your boat, the protection material will no longer react with the saline water or corrode. Once the anode stops working, your vessel will be vulnerable to degradation. Zinc products are highly susceptible to passivation when they are exposed to unsuitable environments. For instance, when zinc is placed in high-temperature water or fresh water, it will passivate and form a calcareous coating. The risk of aluminium becoming passive is low because it is not affected by environmental changes.
Aluminium is a lightweight material in comparison with zinc. Simply speaking, the density of aluminium is much lower than that of the alternative product metal. Therefore, if you choose two products of the same size or volume but different materials, the aluminium will be lighter. This aspect can be beneficial in handling some vessels. On the other hand, if you need an impact resistant anode, zinc is the better choice.
You should consult your sacrificial anode supplier for customised guidance for your needs.