I've tried asking about this on 'tea forums' without much success, so thought I'd try here.
I picked up a Le Creuset enamelled cast-iron tea kettle at a second hand shop for a modest price (I've been kettle-less for a number of years, boiling water for tea in a saucepan). Unfortunately, there is some chipping to the interior enamelled and subsequent rusting of the iron. Le Creuset does offer some sort of guarantee, but in theory this doesn't apply to second-hand purchased items, and anyway I've read that even brand new Le Creuset kettles have problems with interior enamel flaking off, so I'm hesistent to bother with that route. [I don't seem to be losing any more enamel, just continuing to develop rust in the same spots.]
I know with cast iron tea pots the tannins in the tea actually convert the 'red' rust to (less flaky) 'black' rust. So I've tried boiling tea directly in the kettle and leaving it to sit for a few days. This does indeed convert the 'red' rust to 'black'. But after rinsing and boiling plain water a few times, the black rust seems to dissolve and then the rusting problem begins again.
So my question is, is there any way to "fix" the black rust in place, to keep it from washing away? Should I actually 'season' the interior with oil after developing black rust? (Is it worth it?)
