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Alternate solution to Zinc Plating for threaded parts produced to dimensions that don't allow plating [Jordan] 

December 8, 2007

Our Supplier supplied the part to final dimensions without plating Threaded Nut which calls for Zinc Plating Fe/Zn8c2C. Now if the plating is done, then it may affect the final dimensions and the part may not be able to assemble. What can be alternate solution to protect the part from corrossion without affecting the final dimension.

Sanjay Kumar
Product Designer - Amman, Jordan

The parts can be black oxided & oiled or phosphated & oiled, Sanjay, but this will not offer the corrosion resistance of zinc plating.

Ted Mooney, P.E.  finishing.com Brick, NJ

Maybe you could slightly over etch them (after trial and error on samples) to remove one or two thousands per side all around. Clean the smut and proceed with the zinc plating normally.

Guillermo Marrufo
Monterrey, NL, Mexico

Good afternoon:

If I'm understanding your question, this problem is a bit unusual. I usually associate plating buildup and assembly concerns with long bolts and screws, which can build up a lot of plating thickness in the high current density threaded end. Especially with chloride zinc plating. With nuts, the threads usually don't have much plating on them anyway because that's a low current density area.

Maybe this is a longshot, but can the threads on the mating part be roll threaded or cut very slightly undersized to accommodate the buildup on the nut? Maybe we need more information to assist you.

Steve Bizub
- St Louis, MO

YOU have to go to two solution
1- you can confirm on the manufacturing of this to left a tolerance in between 25 to 30 micron less because this toulorence equal zinc plating thickness.After complet plating the dimensions come accurate.

2- If you cant to go to the first solution you can make Blackining or phosphating & oiling. because it will left thin layer on the surface without affecting on the dimensions

Yasser Metwalli Osman
Senior: Chemist

Yasser Metwalli Osman
- U.A.E, Ajman

Hello Mr. Kumar,
I agree that your problem is a little strange. Saying nothing of some kind of misunderstanding, I see two possibilities. Zinc deposition is really too thick (maybe too long treatment) or deposition is right, but your screws are very small, for example 2 mm in diameter. In the second case, 8 microns of deposition should be revised.

Janusz LABEDZ
AUROTECH - Warsaw, Poland

Sanjay,
Screws,nuts and bolts can be batch e-coated in urethane with a deposition of 4-8 microns without blocking the threads or making them difficult to use. Urethane e-coat offers UV stability and corrosion resistance on any conductive metal.

Mike Dywan
PMA Photometals, Inc - Phoenix, AZ, USA