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Removing "water spots" from electroless nickel plated parts

April 6, 2012

Q. Plating & Finishing Experts,

We send out our A360 die-cast aluminum parts for fine blasting with aluminum oxide,then for High-Phos Electroless nickel plating .0015 thick per AMSC26074 [affil link] --Class 3 No Bake. We then assemble the parts into our product and they undergo a 10-hour thermal cycle from room temp. to -10° C to +50° C and back to -10° C then +50° C again.

water spots on electroless nickel plating
The parts must have a very good appearance. We have had several plating quality problems with past vendors, including dark blotchy spots, skip-plating, etc. due to the porous nature of the castings.

We now are using a much better plater, but recently we've been getting "water spots" or small, uniform stains which only appear after our our thermal cycling, on some batches. It is odd, but they are not visible on the parts as-received from the plater. I assume the parts were not hot-rinsed properly, and residual acid or contaminants are wicking out of the pores during our thermal cycle.

I understand you may have advice on the plating process, however our plater is very secretive about his process, and is not very open to corrective actions. I am seeking your help for a solution to rework these parts. We have invested significant labor. Can you please recommend a chemical or product we can hand-wipe the stained parts with, to remove or hide the stains? I have tried Windex Commercial Line [on eBay or Amazon affil link] , but it does not work. The only thing that works is anything with oil. Stainless-steel appliance cleaner (oil-based) works, but is not very healthy for our workers. Even rubbing the stains with our hands seems to hide them. Can you recommend a solution or product that may be less hazardous (more inert) which will hide these stains?

Thank you in advance,

Glenn J
OEM Manufacturing Engineer - San Luis Obispo, California, USA

A. Hi Glenn.
You can try running your stained parts through the Aluminum soak cleaner one more time, with plenty of DI water rinse and spray rinse after that. Good Luck.

SK Cheah
- Penang, Malaysia
April 6, 2012

A. Hello Glenn,
Have you tried a citric acid [on eBay or Amazon affil link] dip followed by a hot DI rinse and dry? I would start out at 10% citric acid concentration. Good Luck!

Mark Baker
Engineering - Mesa, Arizona, USA
April 7, 2012

A. Just an opinion, water droplets left on the surface after a conventional rinse never look so evenly distributed and sized. They look more to me like trapped chemical residues sweating out during the thermal cycle.

Guillermo Marrufo
Monterrey, NL, Mexico
April 9, 2012

April 10, 2012

A. It looks like your spots may well be caused by porosity in the base metal. This can be confirmed by dye testing.

If so, the solution may be to bake the parts before plating in order to dry up any oils in the porosity.

Lyle Kirman
consultant - Cleveland Heights, Ohio

We are facing water stains after electroless plating for particular area; only the parts having blind holes on the surface. So how to avoid water stains?

chandra shekar R
- Bangalore India
July 2, 2013

A. Hello Chandra,
In similar situations such as yours, I have had to employ air agitated rinses, rack agitation / vibration, and ultrasonics to avoid staining that stems from blind holes. It would depend on your racking method to determine which aid would be best. Keep in mind that "outgassing" around blind holes is common in Electroless Nickel, mainly with small holes. What you could be seeing is the out-gassing effect from the plating process itself. I have also used rack agitation and rack vibration in the Electroless Ni plating process. Good Luck!

Mark Baker
- Mesa, Arizona, USA
July 5, 2013

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