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Anodic etching of steel parts, process issues and hydrogen embrittlement issues
Q. We are making a component out of ball bearing steel in which section thickness varies from 0.8 to 3.0 mm.This component is Hardened and Tempered to 700 to 750 HV and Hard Chrome plated to 15 to 20 microns plating thickness. Anodic Etching treatment is done before plating, and stress relieving is done at 180 - 200 °C after plating for Hydrogen De-embrittlement.
WE WOULD LIKE TO KNOW WHETHER A STRESS RELIEVING TREATMENT AS A HYDROGEN DE-EMBRITTLEMENT TREATMENT IS NECESSARY AFTER ANODIC ETCHING, BEFORE PLATING, AS THE SUBSTRATE IS HIGH CARBON HIGH CHROMIUM BALL BEARING STEEL HARDENED AND TEMPERED TO 700 TO 750 HV (60 TO 62 HRC).
IS THE OMISSION OF STRESS RELIEVING AFTER ANODIC ETCHING A CAUSE FOR PLATING DEFECTS LIKE PITTING, PEEL OFF, BLISTERS, etc.?
THANKS.
METALLURGIST - COIMBATORE, INDIA
2005
A. A great deal will depend on your definition of anodic etching. If you are talking about an activation step for the chrome, then absolutely it would not require a heat treatment. If you are talking about a heavy etch today and plate tomorrow, I will question your wisdom, but that is because of my lack of knowledge of your process. Anodic etch generates oxygen at the part, NOT hydrogen, so you can not have hydrogen embrittlement from that step.
A long anodic etch could oxidize-passivate- the part to a point that you could have an adhesion problem. It might also smut the part causing an adhesion problem. For a quality answer, you must provide full details of the entire process. (And then hope that a very knowledgeable person will reply)
- Navarre, Florida
2005
Sir
Are you working on bainite hardened ball-bearing steels?
- Kolkata, West Bengal, India
2005
Q. Can anyone suggest a common set of parameters for anodic etching of steel parts?
We use a 35-40% solution of sulfuric acid, connect the parts to the anode and set 20 ASF for 5 minutes. Then 200 ASF for 1 minute, followed by a cathodic etch at 200 ASF for 3-4 seconds.
Is this similar to what others are doing, and is the cathodic etch necessary, and if so, why?
Senior Chemist - Hampshire, England
April 24, 2008
A. Mike,
Have a look at DEF STAN 03-2, it describes various anodic and cathodic etches, their uses and restrictions. If nothing else it will give you a starting point. You could also have a look at MIL-S-5002, the US equivalent spec.
Aerospace - Yeovil, Somerset, UK
April 29, 2008
Q. I am looking for an article on "The Anodic Etch in preparation for Plating" by F.G. BRUNE & V.L. McENALLY JR.
Can any body help in finding this?
Quality Manager - Etobicoke, Ontario, Canada
January 21, 2009
A. Hi Sunil. That article seems quite difficult to find, but a patent search reveals reference to an article by Brune & McEnally in Plating magazine volume 42, pages 1127-32 (1955), which might be the article in question.
As you see, we appended your inquiry to a thread that deals with anodic etching of steel parts and may be helpful to you. Good luck.
Regards,
Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
July 2013
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