Letter 41042

Hot dipped galvanized vs electrogalvanized  

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Clevis hangers that are to be used to support piping are available in hot dipped galvanized finish or Electro- Galvanized. My question is which coating is the better?

Graeme Mc Dougall
Construction - Austin, Texas, USA

Hello, Graeme. Very similar questions have been asked and answered many times on this site. So if you need a 2nd opinion, patient application of the search engine will yield it, but for a quick answer --

Electrogalvanized means zinc electroplated. Both electroplating and hot dipping can be used to apply a coating of zinc to steel. Zinc electroplating has a definite advantage in appearance and for close fitting parts, but hot dipping will give much better corrosion resistance because the zinc coating will be about ten times thicker.

Ted Mooney, P.E.  finishing.com Brick, New Jersey

I am planning a fence that will incorporate stringer hangers that are either hot dipped galvanized or electro galvanized. Can I use hot dipped galvanized nails with electro galvanized hangers and visa versa?

Daniel Wilkinson
- Boulder, CO, USA

Hi, Daniel. "Electro galvanized" means zinc electroplated. I don't know the origin of the term but it may have simply been an invention by a marketing manager to attempt to ride the coattails of the more expensive and more durable finish through obfuscation :-)

There should be no compatability problem between the two finishes but the electroplated -- oops, pardon me, "electrogalvanized" -- parts may not prove very durable in outdoor exposure as the protective zinc coating will only be perhaps a tenth as thick as the hot dipped coating. There is nothing intrinsically questionable about electroplating; it can be an outstanding finish. But zinc electroplating is no substitute for galvanizing in outdoor exposure. Good luck.

Regards,

Ted Mooney finishing.com Brick, New Jersey

I am re-roofing my house. The local code calls for 8D ring-shanked roofing nails to re-nail the plywood decking which, in my case, is 1/2 inch plywood. The re-roof will be premium material: 30 # standard felt but then 170 # with 250 # in the valleys and at penetrations. Accordingly, I spec'ed premium nails even though roof will be hot-mopped with premium 170 modified SBS underlayment/250 as above and then tile roof. I wanted Maze of Peru, Illinois, double-hot dipped galvanized 8D nails (Maze product # R107A)but it turns out that Maze nail must be hand-driven and my roofer uses an Hitachi 75 AG nail coil gun. He is proposing to use Hitachi ring-shanked diamond point "electro-galvanized" nails---made in the United Arab Emirates. Is this excellent or is there a better product out there for my application which can be used with a coil gun? Or is this UAE-mfged nail a pretty good product? (I recognize it is not as corrosion-resistant as double hot-dipped and CORROSION is my prime quality issue for the nails). Shall I just go with the flow or can I get something REALLY good which works in a gun? The hand-driving will add about two man days at $ 55/hour to my cost (almost $1000) I am told. What should I do?
THANK YOU VERY MUCH!

James Bell
- Naples, FL, USA

Hi, James. As long as this plywood is not pressure treated (and it shouldn't be), and as long as the nails are not exposed, I would think that you can let the builder use the nails that he must use for power tools (hot dip galvanized coatings are probably too thick and drippy to use in these machines). But where you have exposed nails, like the top course of shingles at the peak of the roof, you could ask him to hand drive hot dip galvanized nails.

Regards,

Ted Mooney, P.E.  finishing.com Brick, New Jersey