I recently purchased a Dexter-Russell carbon steel Chinese cleaver, because they're supposed to be amazingly useful.    I'm used to caring for good stainless steel knives, but don't know what special things I should do for carbon steel.  So far, I always wash and dry it immediately after use, and do normal honing/sharpening.    The problem is that after a week or two of use, it is developing spots of rust, deepening to slight pitting.  The rust appears as an orange sheen, and does not disappear readily with scrubbing.    Is this slight rusting normal with use, and will it turn into the patina I've seen on other people's carbon steel cutlery?  What else does one need to do to care for a carbon steel?  I've heard something about oiling and am not sure how that works...  Picture of of edge below, to demonstrate:   
For my carbon steel knives (including my cleaver), I make very sure to wash & completely dry them after use. When I've used it on something acidic, this is especially true. I've never had a problem unless I've forgotten, or haven't completely dried it. When rust does happen in those cases, it's the only time my knife sees the scruby side of the sponge, I use to wash dishes. It comes off easily with that. 