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Pitting of Steel caused by Electroless Nickel Bath



2002

We are having trouble with pitting on carbon steel parts. My plater swears it is coming from the electroless nickel bath not the pretreatment process. The process is soak clean,anodic clean, muriatic acid dip, and electroless nickel plate using a mid-phosphorus bath. Is there any possible way the pitting is coming from the electroless nickel bath?

Daniel Bemenderfer
- Indianapolis, Indiana, USA


First of two simultaneous responses2002

Pits can come from the electroless nickel bath itself.

To be more specific it often is the mid phos EN bath. Your EN supplier will tell you the pits are from rinsing, drag in, cleaners, acid, acid additives, improper filtration, oil drag in, etc. To make things simple heat up a beaker of your EN to plating temp, take a hull cell panel punch a hole in one end, bend 90 degrees hang on a wire or hook, strip zinc coating in fresh 30 % muriatic acid , rinse , wipe with wet paper towel to remove smut and plate 30 minutes to 1 hour. Got pits? Try a different mid phos bath, it can be from the same company. Mid phos baths have so much stuff in them to make them bright and fast that pitting problems can happen with some formulations.

Todd Osmolski
- Charlotte, North Carolina, USA


Second of two simultaneous responses2002

Not very probable. I would check and see if the steel is free cutting or leaded. If the vendor says no, I would send a few samples off for qualified metallurgical evaluation for lead and other alloy materials in it. Some homework with a 10 power lens should give you a good idea of where the problem is and then you can start looking for the cause.

James Watts
- Navarre, Florida


2002

How deep and numerous are those pits, and how thick is the EN deposit. Can it be reasonably established? One way would be to grind or preferably slowly sand off the deposit and see if the pores are still there, then its the steel or the prep cycle. If they are scattered here and there and once the layer is lapped off cannot be found even with a magnifier lens, its the EN out of balance or too old.

Guillermo Marrufo
Monterrey, NL, Mexico


2002

Try switching to a proprietary acid salt for a pickle. HCl has been considered a no/no for EN plating since time began. Forms ferric chlorides that become pits in the plating process. At the very least, put some ammonia in the last rinse before plating to neutralize the chlorides.

Dan Weaver
- Toccoa, Georgia

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