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Masking for zinc passivation

We are manufacturing drawn arc studs. the studs M10*50 are to be zinc passivated except the tip portion of 9 dia and 6 mm long should not be plated. Can we do any masking before electroplating, please do suggest.
Presently we are dipping the completely plated stud in HCl acid to remove the plating in the tip. it is spoiling the stud quality and troubling while doing the stud welding process and giving away.

GOPAL
- India
2005

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Why don't you try putting on a nut on the bolt tip before plating? This nut could be MS or PVC.

Khozem Vahaanwala
Saify Ind

Bengaluru, Karnataka, India

2005

Please define exactly what you mean by "tip".

James Watts
- Navarre, Florida
2005

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Hi James,

If yr counter question was for me, then I meant the first few threads of the stud!

Khozem Vahaanwala
Saify Ind

Bengaluru, Karnataka, India

2005

Yes, it was. I will offer a variation of a previous answer. You might try a nylon nut. They do not like some acids and some caustic solutions, but seal better. If I could afford it, timewise, put two wraps of Teflon tape and then use a PVC nut. You can use a drill motor with a nutdriver to expedite the operation and you can put a filler like rubber tubing inside so it will limit the amount that the nut can be run on.

James Watts
- Navarre, Florida
2005

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Gopal
You may combine suggestions of Vahanwala and James: i.e. you can use a pp mask with a seal. You may face a passivation problem if the seal is not tight enough.As the plating is done for 15-20 minutes the cyanide/Acidic/Alkaline bath solution will seep in through the seal while plating and seep out when out of the plating bath.This will make the passivation peel off or rub off.u may have to introduce an air agitated hot water swill to avoid this.
Meanwhile please be specific as what kind of plating you do. Cyanide/Acid/Alkaline? I can suggest appropriate means.
Good luck

T.K. Mohan
plating process supplier - Mumbai, India
2005

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