Stress Corrosion Cracking In Indoor Residential Pools

Posted on: 19 February 2015

Installing a swimming pool in your home is a great idea, giving you the advantage of exercising at home, relaxing at weekends and keeping the kids occupied. However, many people fall into the trap of ignoring the possibility of damage occurring to the pool. One of the more severe problems that can occur in swimming pools (that can even cause failure!) is stress corrosion cracking (SCC).

Stress Corrosion Cracking

Stress corrosion cracking is a phenomenon that has caused the failure of many recreational swimming pools. However, the mechanisms behind SCC can also apply to residential pools, particularly if your pool is indoors.

SCC is a highly localized form of corrosion that is characterized by fine, hairline cracks that are found around the edges of steel members. The onset of these cracks is very sudden, which means that if they are not spotted then they can quickly cause failure of entire components.  Although the onset of stress-induced cracking can be due to a number of factors, there are three main criteria that dictate the rate at which SCC occurs:

  • The grade of steel used - Some steels are more susceptible than others, and if your residential pool is supported by non-corrosive resistant steels then SCC is likely to occur.
  • Mechanical stress caused by structural loading and/or residual stress present from manufacture and installation.
  • Significant amounts of chlorine in the water. This compound is important for disinfecting the pool; however, if very high concentrations are used then a corrosive film can occur on the surface of the water.

The most important to note is the grade of steel used. The reason for this is that many people believe that simply installing corrosive-resistant steel will stop SCC occurring. This may be the case, but these milder steels may not have a suitable buckling resistance for structural components where fracture could be catastrophic.  If changing the steel won't solve the problem, what will?

Solving the Problem

When it comes to localized cracking, prevention is far better than cure. Making good decisions when designing and installing your residential swimming pool can stop the problem from occurring in the first place. Of course, the first decision you have to make is which grade of steel you will use to support the pool. In this situation, it's best to speak to a professional installation company as they will have experience with this phenomenon and will be able to advise you on a material that is both strong and corrosive resistant.

Once your pool is installed, it's imperative that you monitor the chemical balance of the water. As mentioned, excessive chlorine can cause a highly corrosive film to occur on the water's surface, so learn more and be careful when disinfecting your water. There are a number of chlorine monitoring products available on the market to help you with this.

The ambient temperature of your pool room is also important. High temperatures accelerate the process of corrosion, so you must keep an eye on the humidity of the room. With swimming pools, atmospheric moisture can quickly accumulate due to the water's evaporation. To protect against this, consider installing an air de-humidifier or an alternative way to recirculate the air around the swimming pool.

Finally, as with any piece of equipment, you have to practice proper inspection and maintenance. "Out of sight, out of mind" doesn't apply to swimming pools, particularly where SCC can occur. The onset of hairline fractures occurs extremely quickly, so you have to regularly inspect around your swimming pool to detect any cracks before it's too late.

Don't let bad decisions ruin an otherwise perfect swimming pool. If you do suspect the onset of stress-induced cracks, you should contact a swimming pool contractor immediately who will be able to offer expertise on solving the problem.