Pool Area Corrosion

[johnnydO3]

I am looking for possible causes for above water level corrosion at a few indoor pools. Some are using bromine and others chlorine, but all are on ozone and chemical automation. The bromine pools have contact columns and the chlorine pools have large contact tanks all with off-gassing and destruct. 5 of the pools are in one city with the same equipment in each but only 2 of the 5 have corrosion. The rusting is forming on the stainless gutters and hand rails on the ladders, but again only above the water level in the pool area. There is however corrosion in the mechanical room also of the pools with the problems. In the mechanical rooms with rusting they do have a balance tank in each. Any ideas?

 

[orenda1168]

I'm in the business of recreational water treatment product formulation, production and marketing, and occassionally see this sort of corrosion, principally in commercial pool environments. However, without knowing the specifics of the water chemistry in those cases experiencing corrosion, it would be pure guesswork to identify the problem and its solution.

If you can obtain and post here the chemistry of these waters, including pH, free chlorine or bromine and combined chlorine(chloramine) levels, method of chlorination (bromination) control (ORP, etc.), total dissolved solids, total alkalinity, and calcium hardness. In addition, what other chemical additions are made to the waters on a routine basis, e.g. scale or metal inhibitors, etc., and what is the typical ozone loading, say in grams/hour, and in what volume of water. What is the method for pH control.

I look forward to the data when you can post it.

Orenda

Is there a

Orenda

 

[johnnydO3]

Orenda1168

Pool 2: pH 7.5, Bromine 3.0, Total Alkalinity 80, Calcium Hardness 280. 270,000 gallons

Bromine (BCDMH) tabs are fed via an erosion feeder controlled by automation controller/solenoid valve. pH is muriatic acid fed with a Stenner pump, controlled by automation controller as well. Ozone system consists of 68 grams/hour, 6% concentration @ 56 SCFH (PSA oxygen) I do not have current ORP readings but they were running 680-750. TDS readings were also not provided. They drain the pools once every 3 years The ozone is split into 2 systems with 1 ozone generator's ozone output being ramped by a controller as well. Bather load is a typical high school application. (Moderate bather load)

JohnnydO3

 

[bimr]

Corrosion around swimming pools is a common problem. See the the link from the artice:

http://www.euro-inox.org/pdf/abc_other/SwimmingPoolTechNote_EN.pdf

If you have "rusting" of the surface of stainless steel, it is probably because the stainless steel was brushed or came in contact with a carbon steel tool, which tends to contaminate the surface of the stainless steel.

 

[sbush]

Bimr is right on target! Stainless doesn't rust. Clean off the transient rust stains and they won't return. Check with the gutter manufacturer (Whitten, Paddock, Natare, et al.) for advice on the correct cleaning chemical or compound for your specific finish. Experimenting on your own might void the warranty and/or contaminate the water.

S. Bush

http://www.water-eg.com

 

[kenvlach]

Perhaps "Stainless doesn't rust" ipso facto, but alloys commonly referred to as stainless become non-stainless under sufficiently nasty circumstances.