Well....I had a keratin treatment done OVER a "normal" relaxer after a few months to straighten the new growth and get me away from what is so (not!) affectionately called the "creamy crack." Now, I had not voluntarily relaxed to begin with (long story), so that definitely caused unneccessary bitterness towards the entire process, but after a relaxer in August 09, and keratin treatments (I don't remember the brand, unfortunately) in November 09 and March 10, I was forced to do a BC to try to grow out naturally. And my hair was, once again, about 2 inches long. So...in my experience, it didn't wash out, and it definitely damaged my hair, which it's not supposed to do. But I'm a 3c, so I was much curlier to begin with than it sounds like you are.
Roll Tide!
I was at the 2009 and 2011 BCS National Championship Games

Medium-coarse, super high density, normal porosity, low elasticity.
I'm currently trying out various Curl Junkie and Devacurl products.

Fotki: fotki.com/rolltidegal
password is 'rolltide'