I was onboard this morning doing a few maintenance jobs and going for a motor around the western harbour. Tieing up the spinnaker pole I saw this corrosion in the toe rail. It is evident at irregular intervals around the boat.
I don't believe it is electrolysis or galvanic but!!
It might have been there for a long time but is worse now, coinciding with the increase in offshore sailing.
Any ideas please on what might be causing it?