Cleaning of salt bath nitrided parts

[tactical14]

The company I work for salt bath nitrides ductile iron (80-55-06) parts. I'm having a heck of a time getting these parts clean.

After then parts are pulled out of the salt bath their quenched. They are then wire brushed,then tumbled, then sonic washed and preserved.

It seems no matter how, or how many times, I sonic wash the parts, they always seem to bleed off some sort of "smut". Getting the salt off the part is no problem, it's just this smut that always seems to bleed.

Does anyone have any experience cleaning parts after a SBN bath?

 

[CoryPad]

What is the quenchant after the SBN bath? Is that used just to cool the parts for handling?

I suspect your process produces a fractured compound layer, and along with surface connected porosity in the casting, traps and bleeds various contaminants like salt, water, corrosion products, etc.