Don't Be This Guy

[fstbttms]

Almost two years since the last hull cleaning.

[Hardhead]

Doesn't look like that zinc was doing much. Yikes.

[fstbttms]

Originally Posted by Hardhead

Doesn't look like than zinc was doing much. Yikes.

It had just been installed.

[RaymondR]

Interesting that it had been concentrated in the one short section. Had the section where the anode is installed been painted previously?

[fstbttms]

Originally Posted by RaymondR

Interesting that it had been concentrated in the one short section. Had the section where the anode is installed been painted previously?

I don't believe so.

[Kelkara]

Why has the shaft corroded and not the prop? Assuming it is a bronze prop and stainless shaft (with no zinc), shouldn't the prop act as the anode? Does this imply an electrical problem on the boat, not simple galvanic corrosion?


sorry for the clueless question.

[fstbttms]

Originally Posted by Kelkara

Does this imply an electrical problem on the boat, not simple galvanic corrosion?

It implies an electrical issue for sure. Likely aboard the boat, but not necessarily so.

[ThereAndBack]

Originally Posted by fstbttms

It had just been installed.

That'll fix it...

[letsgetsailing3]

On the other hand, in the future when he's sailing it without a prop, it will be faster.

[TeddyDiver]

Originally Posted by Kelkara

Why has the shaft corroded and not the prop? Assuming it is a bronze prop and stainless shaft (with no zinc), shouldn't the prop act as the anode? Does this imply an electrical problem on the boat, not simple galvanic corrosion?


sorry for the clueless question.

Stainless needs the passivated surface to whitstand corrosion. If that's lost it's anodic compared to all bronze alloys.

[fstbttms]

Originally Posted by ThereAndBack

That'll fix it...

Obviously not but we don't get paid to walk away from a boat, leaving the underwater metals unprotected.

[barnakiel]

Just think of the name. AVILA


Yep. SS lost its noble state and entered its plain vanilla iron condition ;-)


Rare, in fact.


b.

[Montanan]

Okay, so I am bewildered, if the shaft is continuous why would it have corrosion on only the aft segment. It would seem that the electrical potential would be similar along its entire length and the assumably galvanic action would not be so localized.

Can anyone provide guidance as to the causes for the apparent selective corrosion?

[Simi 60]

How's this one for brutal and after only two weeks apparently

This propeller, shaft & stern bearing are off a timber bay cruiser usually moored at Sanctuary Cove Marina. For the 2 weeks while the Sanctuary Cove boat show was on she was moved to Southport Yacht Club. Over the 2 weeks there, she suffered severe electrolysis damage. When the owner went to collect her after the boat show to return to his usual berth at Sanctuary Cove, she had no go …… You can see why.



marine repairs

[barnakiel]

Originally Posted by Montanan

Okay, so I am bewildered, if the shaft is continuous why would it have corrosion on only the aft segment. It would seem that the electrical potential would be similar along its entire length and the assumably galvanic action would not be so localized.

Can anyone provide guidance as to the causes for the apparent selective corrosion?

The part where you scratched becomes less noble, that's where the crater appears. The remaining part is still protected by the layer and does not corrode.



Grab a piece of ss pipe, scratch place in acid. Watch and marvel.


I am not sure if the name is correct but I call it pitting.



b.