How to Avoid Stainless Steel Corrosion in Swimming Pools
Stainless steel has a long and successful history in swimming pool environments. It has a lower corrosion rate compared to other metals and materials, but like all nice things, you must take care of it to keep it looking sleek.
Success is achievable when the right stainless steel and finish are selected, the pool water and air chemistry are carefully controlled, and there is appropriate ongoing maintenance.
Causes of Corrosion
The chlorine-based chemicals used to disinfect pool water produce chloramines, due to a reaction with nitrogen-bearing compounds such as sweat and urine (Yuck!). Chloramines are very volatile and are passed into the atmosphere where they can be deposited onto metal surfaces, decomposing in the condensation to form a corrosive solution.
Repeated cycles of condensation followed by evaporation cause accumulation of these aggressive chloride-bearing compounds on above-water surfaces. There compounds are responsible for the majority of metal corrosion problems found in swimming pool environments.
Corrosion of stainless steel in swimming pool projects is usually cause by one of the following factors (or a combination).
- Inappropriate stainless steel or finish selection
- Inadequate or improper maintenance
- Improper pool fabrication or installation techniques
- Deficient control of water chemistry and the pool environment
The aggressiveness of an indoor pool environment varies substantially with temperature, relative humidity, number of bathers, and the air replacement rate.
Cleaning Stainless Steel
Over-chlorination, inadequate air circulations, or improper cleaning increase the aggressiveness of the pool environment. Most corrosion problems can be avoided through proper stainless steel and finish specification, control of the pool environment, and maintenance cleaning. Cleaning procedures as simple as hosing or wiping down surfaces with fresh water are effective in removing chloride contaminates and preventing corrosion.
When chloramines accumulate on stainless surfaces, superficial brown corrosion staining can appear. This mild corrosion will not impair the structural integrity of the stainless steel surfaces.
One should avoid cleaning products containing hydrochloric acid or chloride compounds, which can cause corrosion or increase chloramine adherence. Steel wool, steel brushes, and steel scrapers not only scratch the surface, but they can also cause irreparable damage by contaminating the surface. A clean, soft, lint-free cloth or sponge should be used to apply the cleaning product.
Very light staining may be removed with a water dampened cloth or with household vinegar or ammonia cleaning solutions (e.g. window and surface cleaners). More severe staining can be removed with mild abrasion household cleaners that contain 200 mesh or finer calcium carbonate. Diluted oxalic, citric, or nitric acid solutions can effectively remove staining and are sometimes sold as stainless steel rust removers. Other acceptable products including household cleaning agents containing citrus oil or silicone spray.
Construction specifier Magazine, Dec. 2005