Electroylis

[Sam Throm]

I have a fiberglass sailboat with an expensive maxiprop. I'm always worrying about electrolysis damage to it. After lifting my overboard zinc I noticed a fair amount of metal had dissappeared. It had been hanging for several months. Out of curiosity I used my multimeter to measure the potential between my zinc and the sea water. (I raised the zinc out of the water and put one probe in the water and the other on the zinc).The result was a voltage of 230 millivolts. Now that I have this number I still don't know what it means. Is this an acceptable potential or is it high? For a comparison I made the same test on a steel hulled boat in the same marina and got a potential well over 1.0 volts. Note: The results were the same with or without shore power connected.

 

[Ralph Johnstone]

I firmly believe .................

....... that galvanic corrosion was created by the Gods of Physics 101 to plague sailors.As a rule, the rates of corrosion and the voltage differentials defy all logic.The best bet is to use an overboard zinc (as you have)and have three zincs attached to your shaft (if possible). And then offer up a sacrifice to the corrosion gods. Regards,s/v Island Hunter

 

[Rick]

Electrolysis

Which way was the current flowing? It makes a difference if the juice was going to the boat (hot marina) or the other way (stray current from the boat).Nigel Calders book "Boat Owners Mechanical

 

[Sam Throm]

Galvanic Gods? Maybe

Rick: Thanks for the link to Surveyer. That will be helpful Ralph: I will continue to sacrifice Zinc to Galvanus ,god of stray electrons. I have two shaft zincs and a prop zinc to offer.