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


-----

Cold blackening stains our hands!

2003

Black colour sticks to the hands on one of our ductile iron parts after cold blackening . Could I know the reason and remedy for it.

Chandra Sekaran
export of engineering goods - Chennai, Tamilnadu, India

Ed. note: Sorry, this RFQ is old & outdated, so contact info is no longer available. However, if you feel that something technical should be said in reply, please post it; no public commercial suggestions please ( huh? why?)

---

2003

Hi, Chandra.

I hope that a vendor contacts you privately with a solution to this problem, but to my knowledge cold blackening involves coating parts with a smutty selenium compound that tends to rub off easily. I'd suggest that the operators wear gloves or that you switch to hot blackening :-)

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey

When we tried initially with hot process we were not able to achieve black colour rather we got reddish brown colour. Can any suggestion be made with process to be adopted to solve the issue.

Chandra Sekaran
- Chennai, Tamilnadu, India
2003

---

Hello, again Chandra. Certainly there are thousands of shops doing black oxiding successfully every day, and it comes out black. And there are many shops doing cold blackening, for whom it is "good enough".

But your questions are a little like saying "my experimental airplane won't fly, can any suggestion be made with process to be adopted to solve the issue." You have told us nothing about your cold blackening process except that it rubs off (which they all do to greater or lesser extent); and you've told us nothing of your hot black oxide process except that the parts came out reddish brown.

Nobody can suggest an improvement to what you are doing until you tell us what you are doing. But your lack of success does suggest that you are employing home-brew solutions. I would suggest, if possible, that you align yourself with a reputable proprietary supplier who will offer you a proven process and work with you. If that isn't possible, and you have a lot of patience, you can search our site where people offer their suggestions for good hot black oxide operation. Good luck.

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
2003