Sound technical content, curated with aloha by
Ted Mooney, P.E. RET
Pine Beach, NJ

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

SUGGESTED GALVANIZING BOOKS
for Engineers, Shops, Specifiers

"Hot Dip Galvanizing of Steel Structures" by Kuklik & Kudlacek (2016)
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"Handbook of Hot Dip Galvanization" by Maass & Peissker (2011)
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"Galvanized Steel Reinforcement in Concrete" by Stephen Yeomans (2004)
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"Hot Dip Galvanizing -- A Guide to Process Selection & Galvanizing Practice" by M. J. Hornsby (1995)
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"Faults in Hot-Dip Galvanizing" by Dietrich Horstmann (in English, French & German)
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"User's Guide to Hot Dip Galvanizing for Corrosion Protection in Atmospheric Service" by NACE (1997 only rarely avail.)
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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?

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.

Regards,

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

adv.
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