is galvanized steel specification different for fresh water and salt water? 2

[delagina]

is this note ok for salt water: Structural steel and plate shall be hot-dipped galvanized, in accordance with astm123.

 

[Ron]

Use the appropriate ASTM specification, such as A123 and then specify G60,G90 or G140 coating weights, tested in accordance with ASTM A90.

 

[delagina]

which coating G60, G90 or G140 do you recommend for salt water? I never specified this coatings before. I have A123 and reading it but would still want an opinion from someone who had specified this before.

Our notes just say: Structural steel and plate shall be hot-dipped galvanized, in accordance with Astm123.

 

[CBEngi]

If its for salt water/marine environment I would use the thickest galvanizing coating.

 

[hokie66]

The problem with specifying the thickness of hot dipped galvanizing is that in order to get it thicker, you have to use thicker steel. The heavier the section, the more zinc it attracts. But I agree, get as much zinc as you can for salt water use.

 

[cvg]

use stainless steel, do not use galvanized

 

[hokie66]

cvg, that is fine to say for small things like connectors, but the rolled structural shapes we need for building big things are not available or economical in stainless steel.

 

[delagina]

I got it. G90 will last 15 years for tropical marine condition.

http://www.galvinfo.com/ginotes/GalvInfoNote_1_6.pdf

 

[cvg]

well, galvanized is fine but if this is a marine environment, you should have a significant corrosion allowance and/or cathodic protection.

 

[DETstru]

If you're doing any field welding you need to tell them to apply cold galvanizing compound to the welded areas.

 

[boo1]

yes use some can cold galv

 

[mike20793]

Watch out for painting hot dipped galvanized members. You need to add in your spec not to quench after it's dipped. The process causes a reaction that makes it very difficult for paint to bond to ithe and blasting it doesn't help.

 

[wannabeSE]

I don't think the Gxxx coating thicknesses in ASTM A653 (sheet steel) is appropriate for structural steel and plates which is typically galvanized per ASTM A123. See

http://www.galvanizeit.org/uploads/...lvanizing_vs_Continuous_Sheet_Galvanizing.pdf

or

http://www.galvanizeit.org/uploads/publications/Zinc_Coatings.pdf

I typically see G60,G90 coatings specified on cold formed steel (metal studs and deck, maybe wood connectors too)

 

[delagina]

Thanks for that info wannabeSE. From my understanding from the graph the minimum is 1 for structural steel in marine environment and will last 20 years. I think my original note is good and no need to add coating specification (Gxx).

 

[SteelPE]

I recently designed a 120 foot tall tower out of structural steel. The client called and said they want to switch it over to stainless as it is in a coastal area. I have a meeting with the fabricator next week. Point being, the members im using are HSS10x's and HSS5x5's and the fabricator says they are available. However, the owners rep says it costs $2.50 per pound which is cheaper than transportation and galv. I don't consider that economical, but the client does.

I just ordered the AISC DG 27 to help with the change over.

 

[kingnero]

Coastal and SS ? What SS exactly?