galvanized bolts 2

[Taro]

Any comments on the pros and cons of hot-dipped vs. mechanically galvanized bolts? The application is statically loaded A325 bolts in a sewage pump station. The bolts will be subjected to constant high humidity and possibly intermittent water contact.

 

[evelrod]

In my experience (several water processing/treatment plants --terd farms--in the L.A. area) the hot dipped variety seem to hold up the best but, bolt fitment and assembly are subject to quality control variations in the mfgr of the fasteners. ie.---for general work I prefer hot dipped and for critical high load assemblies I would use something better such as SS which I find most cost effective in the long run.

Rod

 

[Taro]

Thanks for the info, Rod. The bolts in question are for secondary members such as catwalks, stairs, pipe supports, etc. All the primary structural framing is concrete.

 

[MikeMilburn]

I agree with Rod, hot dipped seems to hold up longer compared to electrically galvanized, the only thing you'll have to ocassionally put up with the odd lump and bump or zinc.
On a somewhat similar note, compare hot dipped to electric galvanized roofing nails,there is no comparison in my mind. I reshingled my roof awhile back and against my better judgement used electric galv nails. Went up in the attic a year or so after and you could see the rust starting whereas the old nails that were in the roof were, for the most part, fine. Just my 2 cents worth....Mike

 

[rustbuster1]

Hot dipped galvanized zinc (HDG) coating is normally thicker than other zinc coatings, especially on a complex surface like a fastener. Life of the zinc is proportional to thickness. Therefore, the zinc coating on hot-dipped fasteners typically last longer.

The class of threads allows for the tolerances for HDG, so this should not be a concern - plus zinc often reduces the friction and makes non-lubricated tightening more predictable.

Tools can damage the zinc - adding a paint or a product like Denso paste can make a big difference for little added cost.