plating, anodizing, & finishing Q&As since 1989
Scalloping In Heavy Electroless Nickel Deposits
We have observed a condition in heavier (>.001") Electroless Nickel deposits which we call "scalloping". It happens only adjacent to masked areas, whether taped or plugged. Plug or tape material doesn't seem to matter. Nylon, neoprene, silicone, EPDM, Teflon, rubber all do it. So far, the only way to avoid this has been adjusting the part design, (i.e. adding a generous chamfer or counterdrill around holds to be plugged. This gets the "scalloping" away from functional surfaces.
The condition appears to be a partial hydrogen pit, sometimes hemispherical, sometimes less than hemi. If parts cannot be redesigned, what would be suggested for a bath modification? We already have an anti-pitter in the Electroless Nickel bath, and never get pits on surfaces that are not adjacent to masking, even in very heavy deposits (>.0025").
- Marlboro, Massachusetts
You didn't mention what is your substrate and prep cycle but is sounds like you need to improve your pretreatments. Plastics, rubbers and other materials used as maskants are hydrophobic. The techniques used to prepare plastics to be plated were developed to deal with this condition and make them hydrophilic, and might help you.Guillermo Marrufo
Monterrey, NL, Mexico
I experience the same thing at times, but it appears also on sharp edges. I suspect stabilizer adsorption here. I'm working on this.Kevin Keating
finishing - Rochester, New York
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