Keel nut galvanic damage or corrosion?
- Thread starter BillyK
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Rust is a form of electrolysis. In that area, the corrosion is likely a result of oxygen deprivation of the metal and if you have anything other than SS keel bolts, they would be similarly compromised.
the bolts are stainless.. i wonder how the oxygen left the water in the bilge.. my stuffing box had a consistent drip so it should have cycled water though the bilge every few days..
Can't tell you definitively if the corrosion is electrically induced, for example from bad bilge pump wiring, or passively because of oxygen deprivation. Keep in mind it's stain"less", not impervious.
Crevice Corrosion
Billy, what ya probably are looking at is crevice corrosion. Water gets between the nut and the washer (the crevice) and cannot easily get out . It loses its oxygen and the stainless can't develop a protective layer. The water becomes very corrosive because of salts in it and eats at the stainless. slow process, but certain if the crevice is not sealed. A Teflon based stuff like MaineSail was talking about in the exhaust pipe thread would be great. Attached picture is a rudder support strap bolt from a buddy's Tartan 37. You can see that the head of the bolt, where it saw flowing water is fine.. and you can see that the shank where the 5200 sealed it off is fine too.. But water was leaking into the crevice under the bolt head and down the shank a little.. You can see just under the bolt head how the shank is reduced to less than half the original diameter.. If ya make sure that the washer, and threads are sealed very well, you will not have a problem.. Make the bolt and nut spotlessly clean before sealing and do not install any bubbles or gaps in the sealant.. Good Luck..
Billy, what ya probably are looking at is crevice corrosion. Water gets between the nut and the washer (the crevice) and cannot easily get out . It loses its oxygen and the stainless can't develop a protective layer. The water becomes very corrosive because of salts in it and eats at the stainless. slow process, but certain if the crevice is not sealed. A Teflon based stuff like MaineSail was talking about in the exhaust pipe thread would be great. Attached picture is a rudder support strap bolt from a buddy's Tartan 37. You can see that the head of the bolt, where it saw flowing water is fine.. and you can see that the shank where the 5200 sealed it off is fine too.. But water was leaking into the crevice under the bolt head and down the shank a little.. You can see just under the bolt head how the shank is reduced to less than half the original diameter.. If ya make sure that the washer, and threads are sealed very well, you will not have a problem.. Make the bolt and nut spotlessly clean before sealing and do not install any bubbles or gaps in the sealant.. Good Luck..
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