Monday, September 28, 2009

Zincs on Mooring Chains

Mooring chains do seem to wear out pretty fast and they are expensive. I am no metalurgist, but when I look at the condemned chain the erosion looks suspiciously as though galvanic corrosion (electrolysis) has been at work. Maybe it just looks that way, but I think the very slightly differing galvanic potential which must exist in the adjacent links (or in the galvanized shackles) is working on the metal.

In another career, a friend was responsible for maintaining moored instrumented sea buoys. He told me that after he started adding zincs to the mooring chains, chain replacement intervals increased by a factor of two, or more. He used a rudder zinc (two zincs connected by a bolt) with brass threaded inserts, and just bolted it through one of the links and tightened it down. As I recall the zinc was located near the top of the water column, which I have often seen is where most corrosion (or wear) takes place .

I mentioned this technique to my mooring company and they were dismissive - and why not? I may try it next season.

1 comment:

  1. Jeff here, another Vega owner. My mooring guy does exactly as you describe. I have all chain to the boat, and he has mounted it on the mooring chain just past the swivel where it joins the riser.


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