chainplates are manganese bronze and were on the boat when I bought her.
During the survey
it was noted that one was cracked but that there was a replacement blank onboard. The PO stated that it cracked when he was putting it on. He didn't have them heated and bent but tried to torsion it into the hull
shape. Manganese bronze as I found out, isn't the ideal bronze for chainplates.
As I was sailing in 30 knot
winds one day (after the replacement of cracked chainplate), I broke a different chainplate WTF, over. A thorough inspection
revealed 3 more cracks in various chainplates.
I'm in a position to stop in Port Townsend regularly and stopped to see Dan at PT Rigging
. He was the first person to recognize that the chainplates were manganese bronze and told me I should speak with Pete at the Port Townsend Foundry and get his opinion.
Long and short of it is that Pete at PT Foundry advises that silicon bronze is the best material for chainplates when it comes to bronze (and all else in his opinion). Stainless when and if it fails, fails catastrophically. There can conceivably be no warning signs of inner corrosion
So, I'm in the middle of replacing all ten chainplates with PT Foundry silicon bronze ones that Pete is making for me. I'm sure he'd be happy to help you find material and discuss better than I can the differences between bronze alloys. He's been outrageously helpful and patient with me.
Anyway, my 2 cents.........