Below Grade Steel

[dodson]

I am looking for a good solution to protecting W shapes below grade. They will be supporting a concrete pan deck cantilevered over a cliff as the foundation for a house (NOT the best idea I know!) Most will start about 8' below grade (attached to rock anchors) then eventually be out exposed to atmosphere. I was thinking epoxy coating or a spray-on bituminous coating. Any other ideas???

 

[JAE]

Here's an older thread that touched on this topic.

thread507-18982

 

[dodson]

JAE-thanks...nothing had come up in my searches but this one will help.

 

[JAE]

The Google Search works better than the Eng-Tips search at this time.

 

[SlideRuleEra]

Hot-Dip Galvanized

http://www.SlideRuleEra.net

 

[dbuzz]

I would recommend two coats of high-build, high-solids epoxy, such as International Paints Interzone 954, to a dry film thickness of 500 microns (~ 20 mils).

 

[sundale]

Maybe an active cathodic protection system?

 

[Lion06]

I agree with SlideRuleEra - Hot Dip Galvanize it.

 

[dodson]

my concern with hot dip galvanizing is that when backfill is compacted on top of the beams the galvanizing would be damaged. I am currently thinking of two options:
1. encasing the beams in concrete

2. Using a combination of active cathodic protection as well as a spray on bituminous coating.

Does anyone know of a good resource for the cathodic protection?

Thanks for all of your responses

 

[SlideRuleEra]

Of course, you should do what you consider best but hot-dipped galvanized steel is self-healing if the coating is damaged (zinc in surrounding areas continues to provide corrosion protection to the damaged area).

It is paint, including bituminous coatings, that fail when the coating is damaged (corrosion begins at the spot of the damage).

http://www.SlideRuleEra.net

 

[apsix]

My preference would be hot dip galvanising (or a good zinc-rich paint) and encased in concrete.

Galvanising is a lot more robust than most paints and provides cathodic protection to damaged areas, as SlideRuleEra pointed out.

I consider active CP overkill for this situation unless it is an aggressive environment.

 

[sundale]

You could oversize the steel section to be able to lose some cross sectional area and still be able to carry the load.