Metal Rescue. It's non-toxic and citric acid based. As long as you get enough to completely cover the knives, just leave them in for a day and all rust will be completely gone. I used to do a bunch of bike restorations and it's like liquid gold for reusing old fasteners and small parts that are unobtainable now.

Of course it doesn't remove pitting, so any substantial rust removed will leave a textured surface. When you're done, put it back in the jug and use it again next time. It lasts a really really long time.