Great find! I would try electrolysis to preserve it. I just started using this method on iron/steel artifacts and have not completed the preservation of anything yet, but it appears to be working well. It is a fairly simple set-up and will be much quicker than just using fresh water, but it will still take at least a couple of months and probably more, to completely remove the salt.
There are a lot of websites that will describe the process that you should check out, but all you need are a large plastic container that will hold the entire anchor under water, some sodium carbonate (washing soda), a car battery charger, and some steel like rebar or wire. (i'm using old barbed wire cause thats what I had)
Put the metal around the edge of the plastic container and wire them together. This process is "line of site" so there needs to be a direct line between the metal and the anchor for it to work properly. Then fill the container with water and add some sodium carbonate. Hang the anchor in the container so that it does not touch any of the metal. Attach the positive car battery connector to the metal and the negative to the anchor. Bubbles will begin to form immedietly. Make sure you have this in a well ventillated area because the bubbles are hydrogen. Let the anchor sit for as long as you can. Since extra electrolysis will not hurt it and it is a fairly large artifact, I would let it sit for at least 6 months.
The biggest obstacles I see you having are waiting long enough, (I know that I am very impatient for the process to finish) and finding a container large enough to keep the anchor under water the whole time. Anyway, good luck and let me know how it turns out.
