"Double-HDG"?

[LCA527]

Does anybody know if this is an actual process for coating steel (double-hot dip galvanizing)? I am trying to find a slightly more economical solution to stainless, and stumbled across this in my research...

Thank you.
JB

 

[kenvlach]

No such thing.* The 2nd dip would melt the outer zinc from the 1st dip. See schematic:

The 2 common methods for increasing galvanizing thickness are 1) Increasing surface roughness, and 2) Using a more reactive steel -- higher Si or P.

For more info, see the Galvanizers Association (UK)

http://www.hdg.org.uk/203_The_Coating.php

See also
American Galvanizers Association

http://www.galvanizeit.org

Galvanizers Association of Australia

http://www.gaa.com.au

*maybe a mistranslation (English-to-Chinese-to-English?) of sheet coated two sides.

 

[EdStainless]

Double galv isn't dipped twice, it has twice the coating weight. As Ken said, selection of alloy, surface roughness, temperature, speed, and galv alloy all factor into coating weight.

What king of parts are you working with? There may be more economical stainless options.

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[LCA527]

Thank you Gentlemen. In my continued research I did eventually find mention of coating weight, which is probably what was meant by that statement. It definitely makes sense anyhow

These parts would primarily be deck hardware and bracketry for a boat yard/launching facility (i.e. forklift stop plates, travel lift wheel guards, pivot plates, etc.). They be boled to a concrete deck, and be in direct and frequent contact/exposure to salt water, sunlight, abrasion, etc. Obviously S.S. 316 would be a great solution for this situation, however, when required plate thicknesses are approx. 0.5-1" (and areas greater than 200sf), it's not something most Clients can afford.

I am thinking that a structural A36 with a "heavy-weight" HDG coating would be the most cost effective solution, while providing similar (if not better) service peformance than it's economic [stainless] equal... I mean, I would get better strength allowing me to reduce the thickness, thus creating a cost savings for the extra surface prep. and heavy-HDG.

What do you think?

Thanks,

 

[EdStainless]

Look into AL-2003

http://www.alleghenytechnologies.com/ludlum/pages/products/xq/asp/P.151/qx/product.html#

This is a duplex stainless grade. It is stronger than either 316 or carbon steel, it is more corrosion resistant than 316, and it costs less than 316.

In places where abrasion/rubbing/wear is an issue look at the AL2003. In other application heavy galv makes sense.

= = = = = = = = = = = = = = = = = = = =
Rust never sleeps
Neither should your protection

http://www.trent-tube.com/contact/Tech_Assist.cfm

 

[LCA527]

Thanks for the great tip EdStainless. I have read through the literature on the AL 2003, and found it very interesting indeed.

Depending on local availability, we will consider this material as a potential substitute for 316 in the future.

Thanks again!