Metal finishing Q&As since 1989

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Hot dipping galvanization of bolts and nuts after electroplated

please I want to ask if possible to re galvanizing bolts and nuts because I have bolts and nuts electroplated but I need it hot dipped, is it possible? tell me how?

Rushdi Al hawary
- Qatar
October 12, 2009

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Hi, Rushdi. It is not a significant problem to strip the electroplating (assuming it is zinc plating) and galvanize an item. However, when dealing with fasteners, hot dip galvanizing is usually so thick that the threads will not work properly unless they were cut to smaller dimensions to allow for the zinc coating.

Regards,

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
October 12, 2009

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Rushdi, the electroplated zinc will be removed in the hot-dip galvanizing flux without any special processing needed.

You can make your bolt threads slightly undersize, as Ted says, to allow for the hot-dip coating.

If the nuts are already in existence, you can hot-dip them and then re-tap. If the nuts don't yet exist, you can hot-dip them as blanks then tap them. Either way, the fact that the nut threads do not have a zinc coating is not a problem, as they will be in intimate contact with the zinc coating on the bolt threads.

Bill Reynolds [deceased]
consultant metallurgist - Ballarat, Victoria, Australia
We sadly relate the news that Bill passed away on Jan. 29, 2010.
October 12, 2009