Dezincified through hull

[Zing]

The boat is a 13 yrs old and there are no records of the type of material used in the through hulls although they should be dzr or admiralty brass. On a recent haul out I took a look at them. There are some pink spots I think. I am concerned the area I looked at is in a protected part of the fitting, covered up by antifoul most of the time. I had to scrape and sand to get to the metal. The bore of the fitting will get more contact with sea water and so may dezincify more I would expect.

Does anyone have any advice for me?View attachment 39696View attachment 39697