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Hot dipped vs. zinc coated bolts

Hot dipped vs. zinc coated bolts

Hot dipped vs. zinc coated bolts

(OP)
I'm not a coating expert - just looking for some wise perspective -

Got an exterior structure, non-marine environment, but outdoors and exposed to midwestern USA summers and winters.

These are mild bolts - A307 or A36, (not high strength A325's) that connect HDG plates to glulam wood beams.  

Contractor wants to substitute a zinc coating instead of hot dipped galvanizing (which we specified) to speed up acquisition time.

I believe, from the literature I've read, that HDG would be much better but just wanted to get some concurrance from you experts out there.  Any comments?  Thanks in advance.

RE: Hot dipped vs. zinc coated bolts

(OP)
...forgot - they stated that they would coat it in two coats totalling 0.001 mils.

RE: Hot dipped vs. zinc coated bolts

In general, plating of fasteners should only be done by the manufacturer for tolerance reasons. Shouldn't matter in your case [especially with only 0.001 mil = 1 micro-inch!!!].

HDG is usually better, but that is mostly due to greater thickness.  Electroplated zinc occasionally has porosity (if buying from lowest bidder), but should be fine if 1 mil thick and yellow chromated.

RE: Hot dipped vs. zinc coated bolts

Mechanically plated zinc, again, with yellow chromate, is fine.

Or did you mean some other type of coating (not plated)?

RE: Hot dipped vs. zinc coated bolts

So these joints are exposed to weather?
There is a chance of water in the joints?
Go with the heavier coating of HDG.
Even those come in grades of coating you know.

= = = = = = = = = = = = = = = = = = = =
Corrosion, every where, all the time.
Manage it or it will manage you.
http://www.trent-tube.com/contact/Tech_Assist.cfm

RE: Hot dipped vs. zinc coated bolts

(OP)
Well, that's the problem, they didn't really specify what type of "zinc plating" (their term) they were going to use.

We've essentially decided to stick to the HDG, but I really wanted to get a quick education on this.

RE: Hot dipped vs. zinc coated bolts

Stick with the HDG bolts. You should have no problem getting HDG fasteners in the materials you are specifying.

The quality of electrolytic or mechanically plated zinc has become a problem lately.  It runs all over the place, the good, the bad and the plumb ugly.   

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