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Acceptable finish on Hot-Dip Galvanized (and Centrifugally Spun) Parts?

June 1, 2010

I am a sales manager for a precision metal fabricator. Galvanizing is a relatively new outsource need for us. One of my customers has designed a weldment requiring hot-dip galvanized finish. The part is a tubular bearing housing (6-1/2" OD x 6-1/8" ID tube welded onto a 5" OD tubular "Saddle") used in solar tracking systems. Recently, the customer has become more concerned with (minor) zinc buildup on the bearing surface of the parts. The zinc buildup causes drag on the plastic bearing.

After several discussions with different galvanizers, I have been told that this is common and not rejectable. Their main concern is not having ENOUGH galv, not having too much. The finish ranges from very smooth to extremely rough, even within the same spin basket.

What type of finish can we reasonably expect from a galvanizer?

Is there another finishing process that may offer similar corrosion resistance to hot-dip?

Tom Sesterhenn
Sales Manager - South Bend, IN, USA

June 1, 2010

Hi, Tom. Galvanizing is a great corrosion resistant finish, but it is heavy and can be drippy, rather like dipping in chocolate. Is there a reason it is impractical to turn or polish the bearing area after galvanizing. Any rough finish like this sounds inappropriate as a surface against which plastic bearings must run.


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

June 3, 2010

Zinc is a very poor choice for a bearing surface, even if it is a very smooth electroplated zinc.

James Watts
- Navarre, Florida

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