I have some Flitz too, but use it only for stainless blades which needs to be shiny.
It cleans a lot. Even a steel silver blade will get brighter with it.
But, carbon builds up a patina, that protects too and costs nothing. I have cut a lot fruits with mine and never had any problems with ´em.
Most important is, never leave them wet at the dishes, like some of our wives do.
In other words: My wife managed it to let our carbon blades rust. Me never.