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Hot dipped Galv. VS. Zinc w/ Clear Chromate

(-----) 2007

I am a novice to the plating industry, but need valuable input from those more knowledgible.

I produce large gutter brackets and now need to produce them in steel. I have received quotes for both Hot-dipped Galv. and Zinc w/ clear chromate. The cost of hot-dipped galv. far more than the other process.

What are the difference in relation to my product ?

They may, or may not be painted, and some will be used in coastal areas (salt sea air) . Does one have better paint adhesion ?

Does anyone know if the other "galv" brackets on the market are truly "hot-dipped" or other ?

Thank you.

Dennis E. Wilson
architect/business owner - Lexington, Kentucky, USA


This question has been asked and answered dozens of times on this site, Dennis, so patient application of the search engine will yield a good insight. But briefly, galvanized coatings are about 10x as thick as zinc plating, and consequently significantly more expensive and corrosion resistant. For gutters that will be painted, the zinc plating may be fine and may give you less adhesion problems. But for gutters that will not be painted, zinc plating is inadequate.

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


As Ted says, HDGalv is much thicker and the corrosion protection is directly proportional to the thickness of the zinc coating.

Most zinc coatings are difficult to get paint adhesion on, and need a competent pretreatment to get adequate adhesion. Paint straight over galv (or Zn Plate) and it will fall off in weeks!
Proper etch pretreatment and you won't be able to get it off!

Geoff Crowley
Crithwood Ltd.
Westfield, Scotland, UK
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