Electrolysis or Stray Current Corrosion?

2010 October 4
by Chris Brown
Shaft Damaged with Electrolysis
Shaft Damaged with Electrolysis

In a prior post “Electrolysis Destroys a Shaft” we cover a story about a 50′ sailboat that almost lost their Maxprop due to a severely damaged shaft.  They were very lucky to haul for routine bottom paint when they did – a few more months and the prop would be gone.

Recently I received an email from Steve D’Antonio suggesting a clarification on the subject.  Steve is an industry expert, frequent speaker and Contributing Editor for Professional Boatbuilder magazine.  Steve writes:

“The entry on shaft electrolysis caught my attention.  Electrolysis is a word the marine corrosion community frowns upon, primarily because it references a chemical reaction rather than carrion per se.  The photo of the damaged shaft is likely a result of stray current corrosion rarer than galvanic corrosion, which anodes would prevent.  No amount of anodic (zinc or otherwise) protection will contend with stray current corrosion for anything more than a short time.  Stray current corrosion results from DC current leaking into bilge water or via an un-bonded through hull.  It typically causes significant damage in a very short period of time, as opposed to galvanic corrosion, this is the kind that is mitigated by anodes, which occurs slowly.  Both are easily identified using a multi-meter, although not always easy to resolve. “


Steve D’Antonio

Steve D’Antonio Marine Consulting, Inc.


I will gladly take feedback anytime from a known expert and update the site in an effort to be accurate and educational.  Thanks Steve!

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