Summary for electroless copper stop-off Discussion
Electroless copper as a heat treat stop-off is raised as a question by Blair Smith, who asks whether electroless copper can serve as an effective maskant for nitride or carburize processes. The only response in the excerpt comes from an unnamed reply, which says it is an excellent question but immediately raises a practical concern: the copper likely needs to be reasonably thick to work, and asks whether there is a thickness specification governing its use. The responder also asks why Blair would prefer an electroless maskant in the first place. Because the excerpt contains no direct test results or confirmed recommendation, the thread mainly highlights uncertainty about copper thickness and suitability rather than endorsing the method.
Q. Has anyone ever used electroless copper as an effective heat treatment stop-off maskant for either nitride or carburize?
Blair Smith
aerospace – Windsor Locks, Connecticut
1996
“Electroless Copper and Nickel-phosphorous Plating”
by Sha, Wu, & Keong
on Amazon
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? Hi, Blair: An excellent question! But doesn’t the copper have to be reasonably thick for it to work? Is there a thickness spec governing this? Out of curiosity, why would you prefer an electroless maskant?
Ted Mooney, P.E.
Striving to live Aloha
finishing.com – Pine Beach, New Jersey
Need quick confidential answers? $25
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1996
Q. Dear Ted:
Yes, typically the copper thickness must be .0007 to .001 inches thick. The more dense the copper the thinner the deposit thickness required. I am not aware of any specification that governs what thickness the copper plate must be in order to prevent heat treat leakage.
The reason for potentially using an electroless copper maskant is twofold. First, very often the areas which require masking (to prevent heat treatment) are internal diameters which are difficult to plate (even with internal conforming anodes). Second, many of our parts have very tight tolerances and an electroless deposit would allow us to use a masked surface as a reference datum from which we could machine away plate from other features which require heat treatment.
Sincerely,
Blair Smith [returning]
aerospace – Windsor Locks, Connecticut
1996
A. Blair,
Semantics: copper does not prevent the heat treatment of steel, it prevents decarburization of the surface of a carbon steel in the hardening process.
Considering the cost of electroless versus modern copper solutions, particularly non cyanide ones, the economics is the cost of masking. Several years ago, my experience with copper from a job shop was poor. We ended up using a salt bath for hardening. Eliminated a number of problems on a complex geometry part. Decarb went to nearly zero.
James Watts
– Navarre, Florida
1996
Q. Hello.
We are Boronizing 4140 steel parts and the customer wants the cylindrical end masked on 3″ of the shaft! We used a water soluble “copper” stop off paste. After boriding, the parts needed to be quenched and tempered. We were told the quench and temper could not be done in a vacuum so the heat treater used no vacuum. We’ve tried everything to remove the stop off but it was extremely hard and left a pattern in the metal? Do you have a better idea? Thanks.
Jim
Jim Dedmon
– Arlington Texas, USA
October 10, 2019