Dont forget to scrub the part! It'll keep looking rusty until you give it a quick scrub and rinse. Im thinking the mix might be off, I use the electrolytic method with perfect results nearly every time with a 10 amp charger. If you have one of the newer 'electric' (computer controlled) chargers, you might not be getting results as the charger will kick on and off because theres no battery. Do you have one of the manual chargers?
The best anode Ive found are old seat frames. Lots of surface area, and when they get rusty, just through them on the ground to knock all the old crap off.
Let us know what you figure out.
Jeff