Painting Metal Deck - Corrosion 1

[bookowski]

I have a situation where we have to use a slab on metal deck adjacent to a pool (i.e. it will form the pool deck). I spoke to Vulcraft and they recommended an expoxy paint over the galvanizing on the deck. They could not offer any specifics though. Does anyone have any experience with metal deck in high humidity environments and recommendations for painting/protecting it? From what I have read painting galvanized is tricky and requires that the contractor understands how to prep the surface very well. I also read that epoxy paints are not recommended for galvanized.

 

[Ron]

bookowski...painting on galvanized metal is difficult and depends heavily on the surface preparation and the type of coating. Epoxy will work but not great...peeling problems.

Get with a quality industrial coating supplier such as Carboline or Tnemec. They have primers and coatings formulated for these applications, but will also place a heavy emphasis on surface prep (pickling, abrasion, etc).

If not an exposed application where aesthetics are issue, I would use an asphaltic coating.

 

[bookowski]

Interesting, I contacted the technical assistance of the American Galvanizers Association and they also recommended an epoxy paint and surface prep per ASTM D6386 for galvanized metal decks. Aesthetics is not an issue, it will be completely concealed. Haven't used an asphaltic coating before - any recommendations for applying this over a galv. deck?

 

[structSU10]

you could design a reinforced slab, ignoring the metal deck, so if it deteriorates its not a structural issue.

 

[TXStructural]

Exposed slabs on deck will corrode. It cannot be avoided, so design it as though the deck is a form what goes away. The other issue is that the deck will retain the moisture that penetrates cracks, resulting in accelerated corrosion of deck and reinforcement. Also, be cautious about the deck funneling moisture down and across supporting beams. I have seen this with installations. To solve the problem above conditioned or other protected spaces, we have designed using a waterproof membrane with a topping slab above the structural slab.

 

[TXStructural]

And here is a link about coatings over galvanizing:

http://www.galvanizeit.org/about-ho...hancements/painting-hot-dip-galvanized-steel/

 

[goMSUfootball]

From your description I am seeing the problem as a metal form being used to cast a swimming pool bottom? If so - Is the pool inside? The steel will expand significantly more than the concrete. Think of a different construction method.

Is the galvanizing gone?
In my experience in a highly corrosive industrial environment:
Paint will peel and fail with steel underneath corroding. Hot dip galvanizing is nearly bullet proof. Cold galvanizing is only for absolutley neccessary touch up. Stainless Steel is great also.
You didn't say if the structure is new? or existing and what the current condition is?

Recommendation:
Hot dip galvanize everything. It is supposed to be self healing.
Use Fiberglass reinforcing instead of steel in concrete.

 

[bookowski]

goMSU - No, the slab on deck is not forming the pool itself. The pool is going inside an existing building, in the basement. It will be on grade essentially. The slab on deck will form the pool deck that is around the perimeter of the pool, i.e. where you walk and jump in to the pool - it will be about 6in. above the water level. In theory the deck itself will not experience any direct contact with water. The environment will be very humid though since it's an interior pool. In addition, I'm sure water will migrate through the concrete at some points and make it's way to the deck.

I think I will follow the advice of TX and struct and assume the deck is formwork only. I may have them paint the deck as well for a redundancy, I would prefer to avoid corrosion wherever possible since it may express itself through the deck or some other manner.