Where the
world gathers for metal finishing
Q&As since 1989


-----

Iron Limit in a Passivate 6 (Hexavalent Chrome) Passivation Bath

I am interested to know if there is a spec. that limits the amount of iron in a passivate bath with hexavalent chromate?

William Grayson
- Santa Cruz, California
2000

---

2000

Doesn't anyone know if there are limits to the amount of iron in a passivate 6 tank ? There is nothing in the spec. but I would think that there would be some consequences if I passivate a stainless part in a bath saturated with iron. Can anyone help?

Thanks,
Bill Grayson.

William Grayson
- Santa Cruz, California

---

I have never seen or heard of any limit. They do reach an ineffective point and have to be dumped. I guess that you use it until you start to have problems with getting stuff to pass salt spray or other required testing.

Actual available acid will gradually lower if your testing is with indicator or a pH of 8 or so as the caustic will precipitate out the iron in the 5-7 range giving a false high.

James Watts
- Navarre, Florida
2000