There was definitely a lot of movement between the shackle pin and it's mounting plate, as we fasten our anchor line to that shackle at times. I have no idea how old the shackle is, but the plate that is is fastened to shows no signs of corrosion whatsoever. Also, being right at the waterline, they are both constantly dipped in salt water. Seems like the perfect environment for corrosion, whatever type it is. I'll certainly check these things more often.
Pacific Seacraft Mariah 31