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Aluminum Vs Zinc

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slickcrafthbc

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"What is better to use; Zinc o

"What is better to use; Zinc or Aluminum anodes.
The boat is moored in the north east. twin alpha ones, 1988 in good condition with stainless props. I need to replace the zinc anodes as they have disolved a great deal. What are the advantages / disadvantages of the two.

Thanks,"
 
"If the boat is kept in saltwa

"If the boat is kept in saltwater, use the zinc anodes. In addition to the zinc above the prop,I put a 3/4" round one on each trim cylinder rod, and since these are rubber mounted I use a copper wire to ground them to the mounting bolts. If you have trim tabs, you should put one one each of those, as well"
 
"Jeff, To really answer your q

"Jeff, To really answer your question. If you use zinc anodes, since they are more electrically active than aluminum, the corrode in its place. If you use aluminum anodes, they have the same "activity" as your outdrive, the only difference is the protection from corrosion your outdrive paint provides. Stick with the zinc!"
 
"You definitely want to stay w

"You definitely want to stay with zinc in salt water. The fact that the anodes have dissolved means they are doing the intended job, and in so doing they are protecting your other outdrive components, which would be much pricier to replace.
Zinc and aluminum are higher in the galvanic series than steel, etc, so when connected to other more "noble" metals in an electrolytic solution (salty water),they become "anodic" relative to the other metals. The other metals become "cathodic". Zinc anions leave the anode and replace the positive ions in the electrolyte, forming zinc chloride salts. This causes metal loss from the anode, but protects the other materials.
You want to use zinc, as it is slightly higher than aluminum in the galvanic series, so it will also protect any aluminum parts, such as props, housing, etc. Otherwise these parts will corrode and dissolve.
Sorry this got a bit long."
 
Zinc is much more expensive th

Zinc is much more expensive than aluminum... so you can see the temptation to use aluminum.
 
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