blade cleaning.. need some advice!!

[zartane]

got this tajong that i would like to share.. the blade is not in good condition, it sort of have a two tones on the blade which the other part is darker (black) as if it was burned or something..

rusted badly and tried soaking it with lime.. but i found out small particals of the blade came of bits by bits, guessing using lemon juice is too hard on the blade which resulted more damage to the blade. so after surfing through this forum thoroughly, i used pineapple juice and its comforting to know that it did not harm the blade.

my question is, how long should i do the process??because every one hour i'll run the blade through tap water while brushing it with a soft brush, it seems like there are black stains coming out from the blade.. its been two days now and the blade still showing the same black stain that smells like burned steel (i guess)..