"I have a substantial corrosion problem with my permanent moorage at Hornby Island that resulted in the grounding of my boat this summer. The corroded shackles were examined by Jan Degroot of Degroot Marine Surveyors who found the extent of the corrosion to indicate the influence of electrical current. There is however no apparent electrical current in the area.

Here is some background information for anyone who might be able to solve this problem for me.

The mooring system was installed in March of this year and my boat broke loose in August. I examined the anchoring system with scuba and found the 3/4 inch swivel shackle heavily pitted and the 1/2 inch crosby shackle so badly rusted that its threaded pin was no longer threaded and would have slipped out if I had not bound it with wire. The 1/2 inch alloy main chain was also pitted as it neared the swivel. The cotter pin in the swivel had rusted out and released the main pin thus releasing my boat.

I found the corrosion on the surfaces of the large shackles to be very extensive for only 5 months and can't think of the cause. The corrosion took place surrounding and including the 3\4 inch swivel located fifteen feet below the surface buoy. The swivel is attached to the boulder anchor by 35 feet of additional 1/2 inch alloy chain chain. An additional 3/8 inch steel galvanized chain runs from the swivel to a second smaller rock to prevent the main chain from fowling on the large boulder. This additional chain is also very corroded near to the swivel. There are no other boats anchored in the area and no know submerged power lines nearby. There is a small stream running into the bay and the bottom is sand scattered with large boulders and some junk such as an old navy anchor, engine parts, old concrete barrel anchor with steel rebar ......

Any help with this problem would be appreciated.

Eric Smith"  email: tropicaltouch@telus.net