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What’s the Best Anode Material?

  • Writer: Marlan Hoffman
    Marlan Hoffman
  • Feb 15, 2023
  • 2 min read


As we walk through the boat yards every fall, it's sad to see all the casualties of the underwater war - saildrives pitted and shedding paint, bottom paint burned near seacocks and folding props that no longer fold. We can blame these losses on one thing: zinc anodes (or lack thereof). Sacrificial anodes are essential in protecting our valuable bits of underwater metal from corrosion damage; they create a voltage difference between them and what we want to keep safe so that electrons force potential damage reactions away from our expensive parts!


Galvanic corrosion is a process that occurs when two dissimilar metals are in contact with each other and an electrical current is present. This type of corrosion can occur anywhere, but it’s especially accelerated in salt water. Sacrificial anodes made from less noble metals such as aluminum or zinc are used to protect the least noble metal in the circuit by sacrificing themselves instead.


Engine-cooling systems, sail drives, prop shafts and outboard engines on boats all require sacrificial anodes for protection against galvanic corrosion due to their aluminum lower units which corrode easily if not protected properly. Boat owners must replace these sacrificial anodes regularly when they have been reduced to half their original size as a result of being eaten away during the process of galvanic corrosion prevention.


Although replacing these sacrificial anodes may seem like a hassle at first glance - it's actually quite inexpensive compared to dealing with potential consequences resulting from ineffective or depleted ones; such as through-hull failure caused by corrosive damage leading even up to sinking your boat on its mooring! So make sure you check yours often and keep them replaced so you don't end up paying for bigger repairs down the road.


In the marine industry, it is essential to use anodes to protect metals from corrosion. Anodes are designed as sacrificial elements and typically made of zinc or aluminum. While aluminum anodes have been found to provide more available electrons for longer life, they can deplete just as quickly due to their greater activity level. Additionally, there is often considerably more marine growth on copper tubes when compared with zinc or other materials used in cathodic protection systems - likely the result of lower copper availability.


The choice between using a lighter weight aluminum anode versus a bulkier zinc one may depend on individual preferences; however, we recommend that only zinc be used for plumbing systems and heat exchangers since its sacrificed ions help prevent biofouling growths from forming over time.. For folding propellers which require extra cleaning assistance due to their design structure, either Sea Shield or CMP/Martyr brand anodes could be considered depending upon personal preference - although we prefer the additional mass of Martyr’s offering given our confidence in its bolting arrangement being better suited for long-term performance than Sea Shield’s option.

No matter what type you choose though - whether it's a lightweight aluminum version or heavier duty zinc variety – having some form of sacrificial protection system installed should always remain top priority when looking after your boat’s components!



See a full report on the experiment at this site: https://www.practical-sailor.com/boat-maintenance/whats-the-best-anode-material

 
 
 

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