Corrosion in pool equipment room

quick answer,

reaction with the chemical,

possible reason

too concentration of chlorides, above 70 degrees F, they become very active and/or

lower grade of Stainless Steel

If possible, increase the air changes per hour. check ASHRAE for "Natatoriums". I can't recall what the recommended number of changes are, but it's high. Also consider a unit that has a "purge" cycle that can be used whenever the pool maintenance people 'shock' the pool with chlorine or other chemicals. Many of the AC units specifically designed for pool enclosures also have the ability to use the hot gas normally wasted to the condensing coils to be routed through a heat exchanger and used to heat the pool. One piece of advice given to me in the past was... "don't let them 'value-engineer' the options on the unit, i.e. the purge cycle, or go with a smaller capacity unit".

Thanks for the info and Happy Holidays

Thanks for the info and Happy Holidays

Thanks for the comments and helpful information. Have a Happy Holiday

galpalrose,

You have "hit the nail on the head", so to speak...

Pool water treatment chemicals are strong oxidizers, regardless of which type you use (solid, liquid, granular, or gaseous)...

And, as you probably know, rust IS oxidation.

There isn't a lot you can do to eliminate this situation, only minimize it. Improve ventilation & housekeeping & try to substitute non-metal items for those that are rusting, wherever possible.

------------------------------------------------------------------------------

(Just my $0.02)

Or move the chemicals elswhere to a place where they will not corrode things. A storage locker designed for such things perhaps?

............or change the metal surfaces for plastic ones?

Thanks to all who have commented Happy Holidays

Just my $0.02 , here , to keep things on the straight-and-narrow, up-and-up, and as thoroughly correct as possible (I detest anything that reeks of "the dumbing-down-syndrome").

Rust is the result of REDOX reactions ... both Reduction (the gaining of an electron) and Oxidation (the loss or giving-up of an electron). Oxidation reactions can ONLY OCCUR (at an anodic site) as fast as reduction reactions occur (at a site that is cathodic, with respect to the anodic site).

Your reference to metal in the pool ... we all assume ... means stainless steel ladders, railings, etc. All stainless steels are NOT alike. Many do NOT do well in chloride environments. Have a corrosion technician take a look at the situation, taking note of everything, including the ppm of Free Chlorine being maintained in the water, grades of SS, etc.

Don't waste your time or money "shotgunning" a solution. Get someone with some NACE training (National Association of Corrosion Engineers International) and get it right the first time.

Best Regards , and Happy Holidays!

ndt-tom,

"to keep things on the straight-and-narrow, up-and-up, and as thoroughly correct as possible "

(I didn't mean to upset you by "dumbing" anything down...)

I do have some familiarity with REDOX reactions, thank you very much...

When "rusting",the iron (Fe²⁺) is undergoing OXIDATION, (becoming Fe³⁺)

What specifically is undergoing REDUCTION, and at what "site that is cathodic" ?

----------------------------------------------------------------------------------------------------------------------

"Your reference to metal in the pool ... we all assume ... means stainless steel ladders, railings, etc."

You should Never ASSUME, especially for other people...

I noted that the original poster (galpalrose), in their message title, indicated that the rust problem was in the pool equipment room, not the pool itself...

no-offense-at-all intended ... It appears that your words:

"What specifically is undergoing REDUCTION, and at what site that is cathodic?" are actually asking a question ... the answer to which is that steel is not at all homogenous. There are miniscule areas (virtually points) scattered throughout that are anodic with respect to adjacent areas (which are thus, respectively cathocdic).

This explains why steel left exposed to humidity/rain etc. will rust even if it is not in contact with any dissimilar metal (which would entail Galvanic corrosion). What is taking place on a lone piece of steel is Local-Cell activity. The anodic site(s) give-up electrons, which travel through the metal to the more cathodic sites. The cathodic sites then "give-up" the extra electrons ... (in the atmoshere, or the splash-zone offshore, the "giving-up" is usually done to oxygen in the surrounding air. Once the O₂ has this extra electron, its affinity for the Fe³⁺ is greatly enhanced...etc).

Regarding the "assume-factor" : BY *stating* it ... ... ... "assumption_negated".

and, in the "For-what-it's-worth" department ~ re-reading the original post, the text (copied-&-pasted here) it says:

"a considerable amount of corrosion has occured on metal surfaces in a newly constructed high school pool (1 year old)" ... This is not worded exactly as in the subject ... Thus, asking for clarification only.

Merry-Happy-Holidays-to-One-and-All !

ndt-tom,

Where in the original post was there any mention of steel?

The original poster referred generically to "metal", and I was talking specifically about Fe²⁺

---------------------------------------------------------------------------------

"Did I miss an earlier :original_post", stating "in the pool equipment room"...?"

Check the title of the original post, and to this forum thread...

"Corrosion in pool equipment room"

While I can't say that I am a frequent swimmer in pools (I personally prefer the ocean), I do not recall frequently seeing metal surfaces in pools, with the exception of the ladders that someone mentioned previously.

------------------------------------------------

About 10 years ago, I was involved with conducting the pre-purchase environmental due dilligence for a shopping center, that had as one of its tenants a health club run by a well known national chain.

The health club had a combined MER housing water filtration & treatment for the pool and hot tubs, as well as the HVAC equipment for those areas. Virtually every metal surface in this room (regardless of the type of metal) exhibited significant rust or corrosion - everything from aluminum, to galvanized sheet metal, to various types of "stainless steel". This corrosion was caused by airborne (vapors) of the pool sanitizing agent (a bromine-based soild pellet-feed system). None of the corroded metals were submerged in the pool, only exposed to the chemical laden air in the equipment room...

These corrosive vapors actually traveled (via a pathway that was not identified) into an adjacent tenant space occupied by a Bank, where they wreaked havoc with their burglar alarm system wiring & sensors.

It sounds as though there is a containment problem in this area. Consider ways of making the containers air- and water-tight. Make sure there is enough free space above the liquids to enable expansion to take place without spillage. Mop up/hose down all spillages promptly and thoroughly.

It is likely that the chemicals being used in your pool are some form of chlorides. I used to do research into mechanisms of rust formation on steel for a steel manufacturer. If you are encountering high levels of humidity and any leakage of the chlorides from the containers into the room occurs, you will almost assuredly have rusting. Any surface imperfections on the steel surface will initially be attacked, but surface rust formation can be self-propagating due to the mechanisms involved.

The other issue is whether the humidity in the room (or the temperature in the piping or other steel fixtures) varies significantly. Once chlorides dissolve into the moisture in the air and come in contact with the steel, rust reactions can start. If the moisture on the steel surface then evaporates because of the formentioned temperature swings, the chlorides at the surface can concentrate and the higher concentrations will affect the reaction rates and increase the rate of rusting.