Thanks a lot for all the interesting input.
@Sajen
Yes, i fear i'm infected... and all because i was looking for a new pocket knife...
The advice of using citric acid instead of pineapple juice is very good. I'm always reluctant to waste the delicious juice.
@Tunggulametung & Spunjer
Electrolysis is of course a very gentle and elegant method of rust removal. On the other hand it is always a big mess and takes some extra effort.
The kris blade has a surface of roughly 400cm^2 if i assume a current density of at least 20mA/cm^2 this would require 8A and for ramp up and closure of the process i would need to be able regulate that current. My lab power supplies won't do, so i would have to build a custom one (not a big deal for me but still some effort).
What current density did you use for your winter project, Spunjer?
For now i still think fruit acid is the most appropriate way to go as the rust isn't as bad as on Spunjers kris. But i will look further into this topic. I have time the kris won't rust away within the next days...
...and if i'm really infected as Sajen said, building a custom power supply will quickly pay off
Best Regards,
Thilo