Etching inconel

[Animasrwm]

Etching inconel using sulphuric acids and a trico ethelyne wash and
vapour degrease to clean.
Noticing a brown water like stain on parts any thoughts

 

[CoryPad]

Possible reaction product between nickel and sulfur (nickel sulfide can be very dark), possibly iron contamination in solvent or water, possible something else...

 

[Animasrwm]

Thanks for that bud