Metal finishing Q&As since 1989
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Anodic alkaline cleaning and anodic acid etching
March 9, 2012
Q. Hi All,
I am considering utilising the following processes for a EP line where the parts to be processed are hollow 304 tubes with cutting geometries formed on one end through grinding and/or laser cutting:
1)Degreasing (coolant) using Anodic Cleaning in a caustic agent
Reason: I am concerned about coolant drying into the parts and also on the ability of ultrasonics to get up the tube (smallest ID 1/16"). The anodic action seems to send O2 bubbles up the tube.
2)Anodic Etching in a sulfuric (10%) electrolyte to remove Fe contamination and Laser cut dross
Reason: It is faster than immersion pickling and avoids HF and Nitric chemicals. I am concerned on attach to the 304 surface.
I would like to gain from other peoples experiences with the above processes both positive and negative
- Ireland
Anodic treatment in both, especially the alkali, will passivate (oxidize) the nickel on the surface of the 304. You need to finish up on the cathodic side to activate (reduce) the nickel oxide, then follow with a nickel chloride (Woods) strike.
Robert H Probert
Robert H Probert Technical Services
Garner, North Carolina
First of two simultaneous responses -- March 14, 2012
Second of two simultaneous responses -- March 14, 2012
Alan,
What is the ratio length/diameter?
Anna Berkovich
Russamer Lab
Pittsburgh, Pennsylvania
March 16, 2012
The ratio varies but 30:1 would be nominal.
Is it the anodic action which oxidises the nickel or the immersion in caustic?
Also if it wasn't deoxidised, what would the implications be post EP? Pitting?
- Ireland
Your plating process on 304 is wrong: try to use catholyte to degrease and activate surface, then deposit Watt's nickel, but the best strike plating bath is NiCl2 +HCl
kevin chiao- Changsha, China
March 22, 2012
March 22, 2012
Hi, Alan.
You might spell out "EP" instead of abbreviating.
I initially thought you meant electropolishing, others obviously thought you meant electroplating, and now I'm thinking you mean electro-pickling :-)
Regards,
Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
Alan,
Electro-Polishing is the best option. Or call it electrocleaning, since it took only one-two minutes to produce clean and deburred inner surface in our Universal electrolyte.
Simple degreasing without electrical current worked fine as preparation before electrocleaning.
Anna Berkovich
Russamer Lab
Pittsburgh, Pennsylvania
First of two simultaneous responses -- March 23, 2012
Second of two simultaneous responses -- March 24, 2012
Apologies for the confusion. I am referring to Electropolishing.
The 2 processes I have asked about are used for
Pre cleaning. One for removing coolant and the other for removing laser dross.
- Ireland
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