Swimming Pool Corrosion and Concrete Staining

Corrosion staining from swimming pool ladder poles was observed on the concrete decking supporting the ladder poles. An overall view of the staining is shown in Photograph A

Photograph A: Overall view of concrete pool ladder support.

The swimming pool ladder poles were removable and were set into a cup receiver as shown in Photograph B.

Photograph B: Close-up view of receiving cup that was a ladder pole receptacle. Note corrosion on inside wall surface of receiving cup.

The poles were chemically analyzed and were found to be type 304L as prescribed in the construction specifications. The bottom of the pole receiving cups, shown in Photograph B, were solid without drainage capability. Thus, chlorinated pool water, which washed into the receiver cups, would remain and concentrate. The bottom of the ladder poles would thus be subjected to concentration cell corrosion and pitting attack by chloride in the swimming pool water.

The rusty corrosion product and concentrated chloride pool water was forced up and around the receiver cup lip and stained the concrete decking.

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Keywords: Corrosion, Concentration Cell Corrosion, and Pitting.