Anode not behaving?

[Conachair]

Anyone had this happen? Just had boat lifted, steel hull, one anode obviously has had a very easy life, looks brand new. All others seem fine(pitting to show they've been working). Using multimeter I couldn't get any continuity between anode and hull. Took it off and same story between anode body and steel strap and even between different parts of the anode body. Gave it a good clean up with an anglegrinder and cupbrush. Same story. Finally got it down to shiney metal using grinder and flap wheel, at last continuity. This was with pushing the meter probes hard into the zinc and scraping them around to try and get a reading but nothing before the flap disc. Almost like it had a protective coating. Now why would that happen? Mg Duff anodes. /forums/images/graemlins/confused.gif

 

[oldsaltoz]

Could it be that it had a connection when first placed that lasted just long enough to allow the surface to deplete enough to prevent very low current flow, then because it was no connected suffered because it was still exposed to normal reaction due to the differential with surrounding material in salt water solution.

A Bit like the reaction you would expect with a salt water anode in fresh water.