They just look a little green? I would not clean that. Bronze naturally oxidizes, and the green discoloration is normal - its natural eventual state. It could even be protective (https://en.wikipedia.org/wiki/Bronze - "Typically bronze only oxidizes superficially; once a copper oxide (eventually becoming copper carbonate) layer is formed, the underlying metal is protected from further corrosion <https://en.wikipedia.org/wiki/Passivation_(chemistry)>.")
Here's a good Cruisers Forum thread on it: http://www.cruisersforum.com/forums/f55/bronze-cleaner-25162.html By the way, you're probably asking about seacocks or sea valves. Thru hulls are the part that goes thru the hull and is threaded into the seacock. If you have proper flanged seacocks, then the thruhull shouldn't be visible at all, except when you're hauled out (and even then it should be coated in bottom paint). On Mon, Sep 4, 2017 at 4:51 PM, <cnc-list-requ...@cnc-list.com> wrote: > > From: Bev Parslow <bparslo...@yahoo.ca> > To: "cnc-list@cnc-list.com" <cnc-list@cnc-list.com> > Cc: > Bcc: > Date: Mon, 4 Sep 2017 23:25:14 +0000 (UTC) > Subject: Stus-List cleaning thru hulls. > Does anyone have a cleaner for the bronze thru hulls? They seem to be > rather corroded. > >
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