Black stain spreading on keris during vinegar cleaning

[jagabuwana]

A word to the wise:

A great regret of mine is opting to use citric acid as opposed to regular white cooking vinegar, on one of my old blades.

It was the first time for me cleaning any blade.

Firstly I put too much citric acid in and it flaked some of the steel off the blade.
It was already in quite a fragile state due to its purported age, and the concentration of citric acid was far too harsh.

For this reason I will always opt to use cooking vinegar and father time.