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topic 6848

Pitting in Acid Copper bath.


I currently have 3 copper baths up and running and plate the same part in all three baths. We know we have small pitting in the surface being plated, but two of the baths do a good job covering the flaw while the third bath looks terrible. All baths have the same ingredients and brightener levels should all be similar.. Any ideas what might be causing this?

Thank you,

Tom G.

Tom Greifenkamp
- Cincinnati, Ohio USA


Without more information, my first guess would be a contaminant. First question: How do the hull cells compare between the three baths (or CVS, or HPLC, or however you control the organics)? Second question: Are you running three copper baths on one pretreatment line, or are the pretreatment lines separate? Third question: How well do the three baths compare electrically? Are there significant differences in the electrical parameters required to get the same plate? Finally, have you tried a designed experiment to nail down the differences (variation)?

I'm sure that there are other branches to this decision tree, but that is where I would start..Good Luck!

James Totter
James Totter, CEF
- Tallahassee, Florida


maybe this will help,

The 3 baths do have the same pretreatment. The bath in question was giving me trouble with pitting, I suspected a contaminant, so I replaced the Copper solution(only 7 gals). The 3 baths are identical.. same size, same setup. I've tried taking anodes from one of the other baths.. still pitted. (Maybe pitting is the wrong phrase.. more like.. Didn't cover the flaw like the other two baths can). Maybe if someone can tell me the what influences leveling, I could start there... thanks again.

Tom Greifenkamp
- Cincinnati, Ohio USA



My first thought was too much chloride, but making up a new bath and having the same problem leads me to think that It would be somewhere else, .....

Are the rectifiers different, If you're actually taking about the deposit is not leveling the same is the thickness of the deposit thinner, different racks and their connections, connections to the anodes, anode surface/ tank, Stray current

Basically I would start back tracking on what is different between the 3 lines.

Chris Snyder
plater - Charlotte, North Carolina


Last titrations gave me the following:

CuSO4 - 206 g/l;
H2SO4- 58 g/L;
Cl - 58 ppm.

All baths are near these levels. We do not control racks so Each rack can be used within any of the three baths. Like I said before, I tried Anodes from one of the good baths, and still no help. I believe the only thing I haven't addressed is the Rectifier.. how can I test if it's giving me what it's supposed to, and could that impact leveling?

Parts plated are all to the same spec.. no matter which bath they are plated in. Thanks for your inputs..

tom greifenkamp
- Cincinnati, Ohio USA


My first thought is filtration. Where are the pits, all over the parts or on the shelf? Try to filter 1 liter on a Watman paper and than look at the residue on the paper.

sara michaeli
sara michaeli signature 
Sara Michaeli
chemical process supplier
Tel-Aviv, Israel


Hi Tom , I trust that you are using some sort of proprietary chemistry , from one of the many supply houses out there ? If not I would suggest that you do so , All things being equal , as you say they are then the answer lies in the tank its construction , what is it made from ? is it a new plastic tank that was not leached before use ? Is there something different about the Rectifier supplying the tank ? If all the chemistries are equal then the answer lies outside the chemistry . regards

John Tenison-Woods
John Tenison - Woods
- Victoria Australia


Hi Tom G !

I wanted to ask a question when your inquiry first came out but felt that my limited 'background' in plating would be, as it sure seems, to be better answered by all the expert opinions you already have.

The last advice from the Land of Oz asked the question I really wanted to ask.... WHAT material is that 3rd tank made from? And then John C.T's query about a new (?) plastic tank that was not leached out beforehand (which I cannot really fathom) infers the lead question of was that 3rd tank previously used for something else and hence one now gets contamination?

All new(ish) plastic tanks (PVC, Pe, PP, PVDF, CPVC etc.) are made from essentially totally inert materials and really should not contribute to problems of your nature. Or am I up a gum tree and you are using fiberglass tanks in which case a scratched FRP tank might harbor contaminants as the material is heterogeneous.

In all fairness to all the people trying to help you, if you succeed in solving your problem, PLEASE let us know so we can stop biting our fingernails.

Cheers !

freeman newton portrait
Freeman Newton
White Rock, British Columbia, Canada

(It is our sad duty to
advise that Freeman passed away
April 21, 2012. R.I.P. old friend).



The things that I would check on a rectifier, is first ripple at your plating amps the more ripple the poorer DC current, I would also check my cables /connections at a given time are the cables connections hotter / warmer than on other baths, you said that the solution in the 3rd tank didn't cover a "Flaw as well as as other baths" Could be like a LCD problem, do the rest of the parts have the same as plated brightness depth of the deposit.


Chris Snyder
plater - Charlotte, North Carolina


We may never get the answer to this one... I've decided to replace pretty much every replaceable component of the bath. Thank you all for your input.

Tom Greifenkamp
- Cincinnati, Ohio USA


Well, I haven't gotten around to replaceing the bath, but have continued to spend extra time determining the problem. One more observation I have noticed.. I've plated a test piece of bronze, smooth finish.. which wasn't apparent before (flaws on flawless surface)! I got extreme pitting on the front side.. but minimal pitting on the back side (part not facing anode.)

Also, I tested fro ripple from my rectifier. I did show what looked to be 5v spikes (words of my EET). But we noticed this in the other two baths.. Is this what is considered a "ripple"?

Latest Titration data after filter and chemical adjustments:

Thanks again.

Tom Greifenkamp
- Cincinnati, Ohio


I like all the input . Switch the copper solution and see what happens.

Gary Patigler
- Richmond Ca.


Sorry I haven't replied in awhile.. Pitting has dissapeared.. along with the solution. I'm assuming a contaminant from drag-in from the past year the bath has been in operation. Baths 2 and 3 started showing early symptoms of pitting so I went ahead and changed them all out. I am keeping the old solution to test when we get the money and/or if this becomes a frequent problem. Thank you all for your support. I do love this site.


Tom Greifenkamp
- Cincinnati, Ohio

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