Identifying a finish and repairing

[CuriousChris]

Im new to hull maintenance.
I have a very small area of rust on my keel and would prefer to patch rather than strip completely.
The paint is a medium grey sort of bluish and is copper if scraped.
I bought the boat with this finish.
I have no idea how to deal with such a repair. Can I sand it and put another coat of -- whatever this is?
The rest of the keel is very good.
Anyone have an idea of what this finish is?
I would rather patch and launch, then later remove this paint properly and replace by a more environmentally friendly alternative.
Help I'm out of my depth.
Christine
Tanzer 22 #866
Sensei
Lake Ontario

 

[Don S/V ILLusion]

My next door neighbor had a Tanzer27 and his keel was iron. If yours is too, it's obviously rust (you knew that!). Just like any metal that rusts, you can't simply cover it over and cross your fingers. The "proper" repair is to sand it to bare metal, coat with an epoxy primer or barrier coat and then bottom paint it. The gray-blue you see is likely the last attempt at this and is barrier coat. Consider yourself lucky it's confined to a limited area.

 

[CuriousChris]

Yes my keel is iron and yes I have a small speck of rust.
I have sanded but I have a copper based finish on there and I don't think very much will stick to it.
The Grey Blue I think is oxidized copper plus "paint stuff".
Any idea what the paint could be.
Christine