Steel Structures and Indoor Pools

[abusementpark]

Do you give any special consideration for a steel structure that is housing an indoor swimming pool?

I have heard that chlorine can cause corrosion problems. Anybody ever dealt with this??

 

[COEngineeer]

If the steel is also exposed to the outside, you will get a lot of condensation on the steel.

Never, but never question engineer's judgement

 

[Ron]

abusementpark...yes, have dealt with this. If the structure is exposed on the inside, you will get significant corrosion from the chlorine/bromine atmosphere (depending on the system being used...both cause corrosion of mild steel)

You have a few choices. You can galvanize the structural components. That will help, but won't stop it completely. You can provide post-erection painting with heavy coating of epoxy. That will help quite a bit. You can isolate the structure by using drywall and ventilation to protect the structure. You can use stainless steel structural components but probably too expensive for the application.

You can also consider a corrosion inhibition system, but keep in mind that the corrosion you will experience will have several forms, not just galvanic (which is helped the most by corrosion inhibition systems).

 

[hokie66]

Hot dipped galvanizing, followed by a high performance coating, probably a urethane, is the usual solution. Suggest you seek advice from one of the industrial coatings manufacturers.

 

[dik]

You can look at a cheap coating system or one that will provide longer term endurance. Coating systems can become very costly for enhanced protection. No coating system is forever, earthling!

For a relatively low cost coating system that will provide some durability, you can use a product similar to Devoe/ICI 'DEVGUARD 4160' with a topcoat similar to Devoe/ICI 'DEVGUARD 4338'. For improved durability, this can be used in conjunction with a zinc rich primer.

An improved coating system can consist of a recommended primer in conjunction with a polyurea coating or a polyurethane with the former generally providing a better coating. Either of these will likely provide adequate protection for many years.

The hot dipped galvanising in conjunction with a polyurea or epoxy is near the upper end and will provide enhanced protection. You have to be careful with the topcoat on HDG; some coatings for a 'zinc soap' (saponification) that interferes with bonding the top coat.

With the exception of the first coating system, the other methods become more costly. Touching up polyureas is generally very good with the new coating chemically bonding to the substrate. Some epoxies and polyurethanes only bond mechanically to a roughened surface.

You can talk to some of the coating suppliers and get a better handle on some of the coating systems and relative costs.

Dik

 

[abusementpark]

Is doing just the post-erection painting with a coat of epoxy a decent option?

The steel in question is pre-engineered metal building framing. The frames are long spans ( about 80 feet).

What is longest member length that can be hot-dip galvanized? There must be a length limitation.

 

[JedClampett]

I've designed several potable water reservoirs with galvanized steel roof systems and standing seam aluminum roofs. In addition, I've inspected reservoirs with galvanized steel roof systems after 20, 30 and 40 years of service. We don't use any other coating. This is a moist environment with a high concentration of chlorine. The galvanized steel performs superbly. The only issue is occasional wear at the attachment of the standing seam roof to the galvanized steel.
As far as maximum lengths for HDG, you can check with your local galvanizing shop. But most of the time, the length is governed by the length of shipping since they can "double dip" a piece and essentially double the usable length of the kettle. I know 60 ft. is not a problem.

 

[hokie66]

Some of this will depend on what is deemed (by the architect or whomever) to be an acceptable finish. Jed and I agree that HDG will protect the steel, but that may not be the "look" desired. Dik is right that you have to be careful with topcoating HDG, especially when it is new. One thing about epoxy topcoats which sometimes gets overlooked is that they don't provide a gloss finish, but rather are chalky in appearance. Repainting over epoxy is also a challenge.

 

[dik]

I like the polyurea coatings... long life, low/no VOC's, tough and durable. The only downside I know of is that they dry very fast - when the spray hits the metal, they are dry!

 

[valleyboy]

Have a look here

http://www.corusconstruction.com/fi...nnovation/Corrosion/corrosion (swimming) .pdf

A UK publication, but obviously the same principles still apply your side of the pond !!

VB

 

[csd72]

All exposed steel should be carefully detailed to avoid ponding.

If you are using steel roof purlins then it is advisable to get ones with the bottom lip downturned.