These are the three through-hull fittings that link the toilet and wash basin to the sea. They are supposed to be shiny and clean.
The two large ones are stainless steel and the smallest is bronze. The large ones have been fixed by galvanised steel nuts which have rusted to nothing.
When I tried to remove the smallest it turns out to be brass. Now brass is an alloy very rich in zinc and this corrodes away in seawater through electrolysis called de-zincivisation. Only the zinc disappears so the metal becomes very weak. I tapped it with a spanner (as you do) and it crumbled into pieces. The pink colour is the brass after zinc loss.
This is not reassuring. If it had broken at sea we would most likely have sunk.
So three new sea-cocks at £150 each! Yuk.
Saving Anne Marie 
De-zincivization sounds like the sort of word I’d make up! Luckily she’s far from seaworthy so drowning by de-zincivization is pretty low down the risk list 😉
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