SailNet Community banner

1 - 18 of 18 Posts

·
Glad I found Sailnet
Joined
·
3,842 Posts
Discussion Starter #1
When looking at a bunch of sailboats while shopping for ours, I noticed that the majority of older boats had rusty keel bolts. One actually had the top layers of the keel bolts flaking off, like beer bottle cap that were gingerly placed back on top. To prevent this, why don't we fasten a small zinc to each of out keel bolts?

The other thing I noticed were engine mounts. The engine mounts on older boats were usually rusty, which meant for a costly repair. Why don't we fasten a small peice of zinc to each engine mount? It would protect the mount and possibly the engine as well.

And I have to believe that the zincs used for such local applications would last a long time.

So there you have my question, why don't we use more zincs in more places?
 

·
San Juan 26
Joined
·
395 Posts
Simple answer is this.
Zincs stop electrolysis, which occurs in the water. Once you remove a piece of metal from the electrolyte, (usually salt water in a boats case) you stop the process.
The corrosion issues you described above are caused by oxidation, so you would have to remove the oxygen from contact with the metal.
This is done on the atomic level by using the galvanizing process or stainless steel.
Hope this answers your question.
 

·
San Juan 26
Joined
·
395 Posts
Simple answer is this.
Zincs stop electrolysis,
Let me rephrase that. Zinc, (or any type of anode) does not stop electrolysis. It merely adds a less nobel metal to the circuit for electrons to attack, reducing damage to the components you are trying to protect.:)
 

·
Glad I found Sailnet
Joined
·
3,842 Posts
Discussion Starter #4
So if your keel bolts are sitting in water, use zinc. If they are dry, paint them.

Is that what you mean?
 

·
Registered
Joined
·
3,336 Posts
Bene,
I think that zinc will protect more noble metals from galvanic corrosion when suspended in seawater, but not from oxidation.
 

·
Owner, Green Bay Packers
Joined
·
1,000 Posts
Zinc anodes depend upon a medium such as water to carry the electrical charge, most commonly in the areas of turbulence around the rudder and shaft. The charged water treats the zinc and the steel as one homogenous substance resulting in the zinc's erosion. It's not the zinc's attachment to the steel that does the job as much as it is it's proximity to the flowing water which imparts a difference in potential or current. That force is absent inside on the keep bolts. The effects are similar but the processes of corrosion are different. Were they similar, your car would come equipped with zinc's and my Green Goblin '97 Ford pick-'em up wouldn't look like a gunnery target.

You can use the product bubb2 lists above or you can just smear some grease on them. If you're picky about your grease, you can use silicone grease, allowing you to eat any french fries you drop on it.
 

·
Registered
Joined
·
5,856 Posts

·
San Juan 26
Joined
·
395 Posts
There is really no need to use it on stainless, since the chemical makeup of stainless already inhibits oxidation. As to why amazon is so proud of it, I haven't a clue. It looks like the same product, but that price is absurd.

I guess there are suckers out there.
 

·
Owner, Green Bay Packers
Joined
·
1,000 Posts
This is also an are where the prep work prior to painting is more responsible than the paint for the results. You can use the liquid galvinize paint but it's not going to do much more for you than any other good paint after scraping, brushing, cleaning and drying the affected areas. While you're at it; a bit of ospho on the rust wouldn't hurt either.
 

·
Ignoring Trolls in 2009
Joined
·
453 Posts


This is what I use. There are a hundred others out there. Flitz, Maguire's, etc. Good Stainless should not rust.
Thanks Mike,
I was just joking, poor reference to the latest anchor galvinized v stainless thread.

Michael
 

·
Tartan 27' owner
Joined
·
5,241 Posts
I thought that depriving SS of air was not a good idea over the long term.
We replaced the aft chain plate on my boat that had stainless bolts encased in fiberglass for 30 odd years. The bolts were unrecognizable as stainless steel and were rusted and pitted.
I have seen the keel bolts on Bene505's boat. The heads of the bolts stick up from the floor of the bilge and there is some slight rusting here and there. The rusting appears to be cosmetic at this point.
I think that Sway means Naval Jelly or phosphoric acid when he says 'ospho' which will remove the rust from the bolts (hardware store, HD etc).
I am not sure whether painting or the use of grease on these bolts would be the best approach. Certainly, keeping the bilges dry would be a step in the right direction. Some solar powered vents might help remove moisture.
 

·
Glad I found Sailnet
Joined
·
3,842 Posts
Discussion Starter #18 (Edited)
Yes Caleb, you are correct. There is very slight rusting on the edges of the stainless steel boats. With all the rusty bolts I've seen, I don't want ours to go that route. If the bolts are wet, then a little zinc would help. If they are dry, then zinc wouldn't hurt. Not sure I want to go with grease for the reason you typed.
 
1 - 18 of 18 Posts
Top