The pre-seasoning is just a good start to a quality seasoning job. I wouldn't recommend cooking acid stews for a while in a new cast iron dutch oven. And I'd cook something else a few times in between the next acidic dish too to build up the seasoning.
As you've discovered, the patina is not impervious to acids. And cast iron is a reactive metal. Build the patina up more and you'll be fine for the occasional acidic dish.
Rub it with a light layer of shortening, or oil. Place it upside down in the oven at 500 for an hour. Let it cool. Repeat a couple of times and it will have a great patina. This does smoke up the house a bit so do it soon while you can still have the windows open. You can also do this on a gas grill with excellent results.
Phil |