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Old 03-15-2012, 12:42 PM   #1
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Is "galvanized" same as "hot-dip galvanized"


A while back, I read that galvanized metal protects against rust, and that hot-dip galvanized goes a step further by helping protect against the corrosive chemicals in pressure-treated lumber. So, I'm at Home Depot this morning and a staff member is adamantly telling me all their lag screws and bolts are hot-dipped galvanized...even though some of them are labeled "galvanized" while others say "HDG".

Was I a sucker for believing what I read? Or was this guy blowing smoke up my chimeney?

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Old 03-15-2012, 01:00 PM   #2
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Is "galvanized" same as "hot-dip galvanized"


Hot dipped is thicker.

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Old 03-15-2012, 03:22 PM   #3
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Is "galvanized" same as "hot-dip galvanized"


Galvanizing is the process of applying a zinc coating to steel. There are three common techniques used to galvanize steel. One is hot dip galvanization, which consists of applying the zinc coating at a relatively high temperature (hence the term hot dipped). A second technique is electrogalvanization, which is a form of electroplating, where the zinc is deposited by electrical charge. A third technique is thermal diffusion galvanizing, which applies the zinc as an alloy using powdered zinc.

For outdoor use, hot dip galvanizing is required, as electroplating (which is cheaper) does not produce a thick enough coating, and further does not produce a coating of zinc oxide. You can tell the difference between electroplated steel and hot dipped steel very easily. Hot dipped steel is dull grey, whereas electroplated steel is shiny silver color.

Two things to know. First, do not purchase electroplated steel for outdoor use. Second, never believe anything anyone tells you at a big box store.
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Old 03-15-2012, 03:48 PM   #4
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Is "galvanized" same as "hot-dip galvanized"


......... everything he said plus, never use anything but hot dipped galvanized fasteners in treated lumber. (unless you use stainless steel of course)
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Old 03-15-2012, 03:57 PM   #5
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Is "galvanized" same as "hot-dip galvanized"


Hot dipped galvanized can also appear "runny" for lack of a better description.

The racks on our work trucks are fabricated in our shop out of tube steel, relief holes are drilled to keep the metal from expanding and the entire 20x8 rack is dipped in a tank. The finish is practically indestructible, looks good and lasts at least 5 years.
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Old 03-15-2012, 03:58 PM   #6
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Is "galvanized" same as "hot-dip galvanized"


Thanks, Daniel. That was very helpful and it cleared up the confusion. Here's where I think this ends up:

1. Those shiny fasteners that say "zinc coated" and which everyone knows not to use in exterior applications...those are also technically "galvanized" fasteners, even though they're not referred to as such on the shelves.

2. Stores, in general (not just Home Depot, from what I've seen) seem to have hijacked the term "galvanized" to exclusively mean "hot-dip galvanized". Evidence to this are all the dull-gray fasteners that are labeled simply "galvanized".

3. For god knows what reason, it seems Home Depot likes to confuse people. Sometimes they'll use "galvanized"; sometimes they'll use "hot dip galvanized" or "HDG". Please. Pick a term and stick with it. At least when you're describing items on the same shelf!

In this case, it seems Mr Home Depot man was right--all the dull-gray fasteners are HDG.

Does that sound about right to you?
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Old 03-15-2012, 04:47 PM   #7
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Is "galvanized" same as "hot-dip galvanized"


The shiny fasteners could be ordinary steel, stainless steel, or electroplated galvanized, based strictly on color. The fact that they say zinc coated, if you believe the label, indicates they are electroplated galvanized, not suitable for outdoor use.

As to the store use of the term galvanized, it technically includes all forms of zinc deposition. If the stores elect to apply it only to hot dipped fasteners, well I guess that is their privilege, but it is not accurate. Well what else is new. By the way, just to add to the confusion, hot dipped galvanized does not tell you how thick the zinc coating is. Thicker is generally better.

For example, Simpson makes steel brackets with three different levels of galvanization. The "standard" galvanized bracket is called G90 zinc coating, and it is not suitable for outdoor use. Then there is ZMax, which is technically described in the Simpson catalog. This is a hot dip galvanized bracket. Then there is HDG, which of course stands for hot dip galvanized, but curiously it uses A DIFFERENT procedure than ZMax fasteners, and is apparently more resistant to corrosion than ZMax. Go figure.

This is all very confusing, not the least of which is that Simpson has an entire section in their catalog explaining that they are unable to offer useful advice on which type of fastener to use with modern ACQ treated lumber, which of course is about all you can get. I guess you could use all stainless, maybe you should mortgage your house first.
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Old 03-15-2012, 05:03 PM   #8
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Is "galvanized" same as "hot-dip galvanized"


Ha! Yes; I've read the Simpson disclaimer before. Talk about trying to play it safe! They should start with: "Here's three thousand words, and a chart, to let you know we think we know what you should use, but we're not really sure, or at least our lawyers won't let us tell you."

Oh and yes...when in doubt, use stainless steel. That's like saying: when in doubt, buy pure-platinum silverware. It'll go well with the yacht and private jet.

So, it sounds like we're in agreement. The stores are just confusing everyone by referring to HDG as simply "galvanized". At least it's not as bad as a term that is outright lying--like "lag bolt".
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Old 03-15-2012, 05:39 PM   #9
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Is "galvanized" same as "hot-dip galvanized"


The confusion of terms leads to some unfortunate problems.

"Galvanized" steel studs can rust when pierced by screws when they strip the protection from the studs and screws that and gives the moisture a chance to promote deterioration.

Any time you a two threaded pieces connected, it is possible to remove the galvanizing coating.

Dick

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