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Ted Mooney, P.E. RET
Pine Beach, NJ
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for Metal Finishing since 1989
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Orange tint after passivation
July 21, 2011
Q. Hi friends
We are producing cannulated medical parts (stainless steel), but we are getting some orange tint inside the cannulation after the passivation process.
Could you please explain why is this happening?
Ultrasonic cleaning is not enough to clean this effect
Could you suggest some method to eliminate or prevent this orange stuff?
Problem: orange color inside cannulation?
Brainstorming
Could you please input additional causes?
-Passivation residues ( nitric acid /citric acid )
-Not properly neutralized passivation
-Not properly passivated (oxidation)
-Not enough passivation inside the cannulation
-Final cleaning residues
-Tap water after rinsing
- WEST BABYLON, New York
A. Frank,
Could you provide some further information? What grade of stainless steel are these parts, and what passivation process are you using, including acid type, concentration, temperature, and immersion time?
I'm also having trouble getting a mental image of your parts, in order to suggest reasons why the discoloration is only happening inside the cannulation and not on the entire part.
Ray Kremer
Stellar Solutions, Inc.
McHenry, Illinois
August 16, 2011
Q. Hi,
I am experiencing a similar problem. I see an orange tint inside the part after passivation. The parts are passivated in a nitric acid solution with sodium dichromate as post treatment process. Orange tint is seen only after sodium dichromate treatment.
- Bangalore, India
July 23, 2013
A. One need only look at the Wikipedia page for "Chromate and dichromate" to see that the characteristic color for dry dichromate salts is an orange-red. Perhaps you are not rinsing well enough?
Ray Kremer
Stellar Solutions, Inc.
McHenry, Illinois
July 30, 2013
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