J/30 Class Association Forums J/30 Forum The Boat, Sails and Equipment Miscellaneous parts thread

Vic - Stainless does not mean it won't rust. You are seeing evidence of a possible combination of:
1. Substandard quality steel (e.g. maybe cheap Chinese knock-off without quality control for the alloying process)
2. Stainless immersed in water with no oxygen

Stainless works if there is a source of Oxygen, e.g. areas that get wet and dry or are permanently dry. Otherwise you get accelerated crevice corrosion because there is no oxygen source to continue to build the passivation layer.

With the wet core, the ss bolt was in constant contact with a source that had no oxygen, hence the result you see in the picture. More reasons to make sure all holes are epoxy isolated!

That is a reason that Monel and Marine Bronze is better suited for use below the waterline.