Metal finishing Q&As since 1989

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Acid Zinc sulphate throwing power additives - need info

2005

We're working with a simple acid zinc sulphate solution with no organic additives. Throw into recesses is poor while plating thickness at protruding edges (or any high current density area) can be 2 or 3 times the average thickness. We have used a mixture of shielding and auxiliary anodes to improve conditions but still come up a little short with overdeposits in some places and not enough metal in others.

As such, I am considering experimenting with additives and I am looking to pull together a list of likely candidates with some notes about their general effect and any other useful related info. I collected some info on 2 additives from an abstract I was able to pull up on Google (but I haven't coughed up the $25 for the full paper yet -- Journal of Chemical Technology & Biotechnology Volume 75, Issue 8). Here's an example of what I am hoping to pull together:

Additive - Effect - Typical Concentration Range - Comments
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dodecylbenzaenesulfonate (DBS) - can improve throw up to 4x - ? - ?
4-methoxy aniline - can improve throw 1-2x - ? - ?
? - ? - ? - ?....

An ideal additive would be one that is effective at very low concentrations since it is important that the additive(s) NOT be incorporated into the deposit to any great extent. All information and any suggestions would be greatly appreciated.

Regards,

Thomas Hanlon, Materials Engineer
aerospace finishing - East Hartford, Connecticut, USA