Miracle Cast Iron?

So a few months ago I was at a store, and they had a bunch of Cast Iron "Teapots."  Normally I would write these things off right away, but upon further inspection of some of them, I came to realize these were not the lined cast iron Teapots.  Even more confusing I imagine they would make horrible teapots even though they came with infuser baskets, as I can't help but think if moisture was left inside them for an extended length of time they would rust horribly.  These were such bargain priced I decided to grab one to experiment with it as a kettle.   It has started to rust ever so slightly on the inside, and is gathering a little bit of white frosty build up on the inside.

But what teas should I use the kettle for when brewing?  This is a quite hard choice, as even inside similar categories I have gotten wonderful and not so great results between similar teas.  For example I tried it with my last bunch of The Tea Galleries Iron Warrior Monk, and it was phenomenal, I tried it with Red Blossoms Tie Lou Han, and while it had a similar effect by making the body much more pronounced the flavors seemed quite off.  The same thing has happened with some Sencha sometimes it is wonderful, other times with different teas some of the major notes of the teas seem horribly off.  They also seem to be off in interesting ways, like sometimes the tea tastes almost hollow,  in the sense that if the taste of a tea is a large painting sometimes it almost is like a cannon ball had been fired through the painting.

In full disclosure, I hope to elaborate on this more in the future, and one thing to consider is I have been eating a lot more Indian food, and it is entirely possible that on certain days the spice pallate I am not entirely used to has altered how I taste teas on those evenings.