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Aluminium anodes have a capacity of 2,700 Ah/kg, significantly higher than zinc anodes, which provide 780 Ah/kg. However, aluminium anodes are 88% efficient, slightly less than zinc’s 95% efficiency. Aluminium is approximately 2.5 times lighter than zinc. In practical terms, a 10 kg zinc anode can be replaced by a 4 kg aluminium anode of the same size, offering equivalent or better anodic protection.
Economically, aluminium anodes provide significant advantages. They allow for a 600 kg weight-saving for every ton of zinc anodes replaced, increasing cargo capacity. Since 2005, the cost of high-purity zinc has risen by over 200%, making aluminium anodes the more economical choice. They are priced similarly per kilogram but require only 40% of the weight for the same level of protection.
There are some restrictions on aluminium anodes. They cannot be used in tanks containing flammable substances due to sparking risks, where zinc anodes are recommended. Additionally, aluminium anodes are unsuitable for aluminium hulls or components because the electrical potential between the anode alloy and the aluminium is insufficient for protection. Despite this, zinc and aluminium anodes can be safely mixed on the same hull.
Overall, aluminium anodes are a cost-effective, lightweight, and efficient solution for vessel protection, outperforming zinc anodes in most applications except where specific restrictions apply.
Zinc and aluminium anodes are manufactured to meet the United States Bureau of Ships Military Specification MIL-A-18001K for zinc and US Military Specification MIL-DTL-24779A (SH) for aluminium as follows:
| Al | Cd | Fe | Cu | Pb | Other | Zn |
|---|---|---|---|---|---|---|
| 0.1 - 0.5 | 0.025 - 0.07 | < 0 .005 | < 0.005 | < 0.006 | < 0.1 | Balance |
| In | Cu | Si | Fe | Zn | Other | Al |
|---|---|---|---|---|---|---|
| 0.014 - 0.020 | < 0.004 | 0.08 - 0.20 | < 0.090 | 4.0 - 6.5 | < 0.01 | Balance |
We offer an extensive selection of Weld-On and Bolt-On Zinc Anodes, along with Aluminium Anodes, available in a variety of shapes and sizes. Our inventory includes the most commonly stocked sizes, ranging from 1.5 kg to 10 kg for both zinc and aluminium anodes. With hundreds of options to choose from, we can source anodes tailored to meet your specific requirements.
Contact the Supa Marine Paints team today for unmatched guidance on all your coating needs and marine anodes. With a wealth of knowledge and years of experience, our certified professionals are here to ensure you get the best solutions for your projects. Reach out now and experience the difference expertise makes!
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