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Difficult copper plating applications: tiny I.D.s, and inside of slots

Q. I would like to copper plate (both internal and external) 1028 DOM steel tubing, during the development of a new product. The I.D. of the tubing is .250" and they are 4" long. Can I do this with a "safe" electroless process? If so what would the electrolyte be? Thank you again. Mark

Mark Robidoux
- malvern, Pennsylvania

A. It might plate the full length of the ID if you used a proprietary "high Throw" EC. Safe is a very subjective word. An insurance company would not think that running an electroless copper line was very safe, especially with no prior experience. Your workman's comp will probably go up several percent.

James Watts
- Navarre, Florida

A. One option you could use would be to Brush Plate the ID of the tubes. With Brush Plating you don't have tanks or the insurance costs that go with them.

David Crocker
- Valencia, California

I have done a fair amount of brush plating and would like to see the anode and wrap that can plate the inside of an 0.250 tube that is 4 inches long with a low end of the pay scale machine shop person doing the work. I would like to do a metallographic cross section before I will say it is equal to a electroless copper plated part with lots of agitation from the bottom of a vertical tube.

I also think that in most states, a plater and a brush plater are considered to be in the same category, IE: a generic one.

It is true that the volume of the solution is less and the hazardous waste should also be less.

Brush plating has many very good applications, I just do not think that this is one of them.

James Watts
- Navarre, Florida

We have plated silver on stainless steel tubes with a diameter of .5 inches and a length of 4 feet for the U.S government with excellent adhesion to the base metal. These parts were cross sectioned and passed all their testing. Brush plating was not their first choice, but it is the only one thats works for them. As for the anode, we have various types and styles the smallest anode being .020" in diameter.

David Crocker
- Valencia, California

I have to agree with James Watts on this one. Yes, perhaps the component could vaguely be brush plated; but it also could be tank plated with an auxiliary anode; it could also vaguely be electroformed from a layer of copper, followed by a very heavy layer of iron plating followed by another layer of copper; and there are other vaguely feasible approaches as well. But the inquirer asked whether simple electroless plating sounded feasible--indeed it does, and probably more practical than the alternatives. The difference in the 'safe'-ness of brush plating vs. tank plating seems pretty slim to me, but see letter 3243, "Exceptions from Pretreatment Regulations for Touch-Up Plating Operations" -- could be there is a difference.

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

Q. I am looking to plate copper on a steel grade 440C shaft. The copper must be deposit in slots machine length wise on the shaft. Slots are 2.5 mm width, 1.5 mm height and 40 mm in length. Overall length of shaft is 150 mm. Diameter is 35 mm. I need the copper to completely fill up the gap in slot. This is a design requirements for this shaft to work as squirrel cage.

Looking for a process to do this.


Vincent Ho
- Singapore

A. A problem with a project like this is that you end up trying to simultaneously develop a new technology approach to push forward the art, while you are simultaneously learning the basics of the required processes to do it as a beginner with no experience :-)

The thing to do is probably to decide on a technology and send the project out to people who are skilled in that technology. I think if you send it to a highly skilled and experienced electroformer, they may take a few days to get it right with all their skill and experience, or to tell you it can't be done; but if you try to do it yourself, it will be years before you even know if the problem is the limits of the technology or the lack of knowledge of a beginner.

Send it to a top notch electroformer.

Guillermo Marrufo
Monterrey, NL, Mexico

A. Electroform it

Russell Richter
- Danbury, Connecticut, USA

A. Hi,

Your design seems to be a good candidate for other process than plating. Plating is most inefficient trying to fill recesses, holes or anything similar. You probably would like to investigate sintering, a powder metallurgy process at very high pressures and moderate temperature where the layered metal is provided in powder form. This is very common for complex shapes of copper and other expensive metals and alloys,


Guillermo Marrufo
Monterrey, NL, Mexico

A. Hi Vincent, It sounds like you are trying to make an air bearing spindle although 35 mm is a bigger diameter than most on the market which are commonly used for dicing, or drilling printed circuit boards. So maybe you have a new application? Electroforming is the way to produce them, but you need top quality copper and adhesion otherwise it could fall apart when it rotates. What speed do you intend to rotate this shaft at? I know it is possible with small spindles to go up to 300 K RPM, but with 35 mm diameter maybe only 60 K RPM is needed. And yes it is possible to fill the grooves all the way up!

Wendy Chilton
- Chester, Cheshire, UK
October 3, 2012

Q. Can I use stainless steel wire as an anode when plating copper?

I am copper plating the I.D. of a 10 cm diameter tube that is approx. 100 mm long.

I am stringing an anode down the center and pumping a copper solution through it.
The anode is copper wire twisted together to make a sturdier anode that is straight.
That anode gets depleted after three hours and can cause a short when it gets too thin and then touching the inner wall of the tube.

If I use a copper anode outside of the tube to keep the copper solution from being depleted (the solution is pumped out of that bath and then pumped into the tube), can I thread stainless steel wire down the center of the tube and forget about the wire getting thin and possibly causing a short? Using the copper solution to plate the tube's I.D. instead of copper wire anode?

JB Coulter
- Visalia, California USA
January 27, 2020

A. Hi JB. I'd say that yes you can, but two provisos. First, stainless is probably okay for cyanide and alkaline copper, and probably not okay for acid copper. Second, the current carrying capacity of stainless steel is probably 10 percent or less than that of copper^only 10 percent that of copper, maybe less, so it will probably need to be substantially heavier than it was when it was copper.


pic of Ted Mooney
Ted Mooney, P.E. RET
Striving to live Aloha - Pine Beach, New Jersey
February 2020

thumbs up sign Thanks for the reply.
There's always a gotchya.

JB Coulter [returning]
- Visalia, California USA
February 5, 2020

A. Use stainless steel and "neckless it" with plastic balls to keep it from shorting, increase the copper content of the solution, increase the pump flow.

robert probert
Robert H Probert
Robert H Probert Technical Services
supporting advertiser
Garner, North Carolina
February 6, 2020

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