Aluminum anodes are rapidly replacing zinc anodes for cathodic protection of ship hulls. With the advent of alloys recently developed by the U.S. Navy, aluminum anodes are very different from those used for hull, outboard and stern drives. These aluminum anodes have better electrical activity and protection than zinc, plus they last longer, and for many years aluminum has been used in Marine engineering to protect equipment that requires long-term corrosion protection. Aluminum anodes also use a much less toxic activator, which makes them more environmentally friendly. On top of that, aluminum anodes are really the only option for saltwater environments. So, if you park your boat in a place where fresh and salt water mix (such as a river mouth that flows into the sea), you should definitely use an aluminum anode. Aluminum anodes have become a choice for the U.S. Navy, as well as large commercial fleets, because they save money (aluminum anodes last longer, so vessels take longer to replace) and because aluminum is very light and can provide better fuel economy in larger fleets.
Chemical composition of aluminum anode
| Types | Zn | In | Cd | Sn | Mg | Si | Ti | Impurities, not more than | Al |
| Si | Fe | Cu |
| Al-Zn-In-Cd | 2.5-4.5 | 0.018-0.050 | 0.005-0.02 | — | — | — | — | 0.1 | 0.15 | 0.01 | Balance |
| Al-Zn-In-Sn | 2.2-5.2 | 0.020-0.045 | — | 0.018-0.035 | — | — | — | 0.1 | 0.15 | 0.01 | Balance |
| Al-Zn-In-Si | 5.5-7.0 | 0.025-0.035 | — | — | — | 0.10-0.15 | — | 0.1 | 0.15 | 0.01 | Balance |
| Al-Zn-In-Sn-Mg | 2.5-4.0 | 0.020-0.050 | — | 0.025-0.075 | 0.50-1.00 | — | — | 0.1 | 0.15 | 0.01 | Balance |
| Al-Zn-In-Mg-Ti | 4.0-7.0 | 0.020-0.050 | — | — | 0.50-1.50 | — | 0.01-0.08 | 0.1 | 0.15 | 0.01 | Balance |
Electrochemical performance of aluminum anode
| Performance, types, indicators | Open circuit potential
-V(SCE) | Working potential
-V(SCE) | Actual capacitance A · h/kg | Current efficiency
% | condition |
| Ordinary aluminum alloy anode | 1.10-1.18 | 1.05-1.12 | ≥2400 | ≥85 | Corrosion products are easy to fall off and dissolve evenly on the surface. |
| High-efficiency aluminum alloy anode | 1.10-1.18 | 1.05-1.12 | ≥2600 | ≥90 |
| Highly activated aluminum alloy anode | 1.45-1.50 | 1.40-1.45 | ≥2080 | ≥70 |
