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Aluminum pool coping is pitting and rusting

May 5, 2010

I have an In-Ground pool with a vinyl cover and aluminum coping. The pool is only two years old and when opened this spring, we noticed that the coping is pitting and rusting. The pool installer, (who comes highly recommended) is not sure why this has occurred. He checked with the manufacturer again without an answer. It was believed that the bonding or a low frequency could be the source of the problem; however, the pool company came to the house and could not find a problem. At this point they want to sand and repaint the coping, but we all want to know what the root of the problem is prior to repairing the damaged coping. Thank You In Advance!

Dave Aldridge
Homeowner - Butler, Pennsylvania, USA
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May 7, 2010

What's puzzling me is the fact that aluminum doesn't "rust". Aluminum oxidizes white.

Do you have hard water where you live?


This sounds like rust is precipitating onto the coping, or the coping may not be aluminum.

Robert H Kinner
- Toledo, Ohio


May 14, 2010

Robert, thanks for your response. I meant that the coping is oxidizing rather than rusting. We have city water. It is pitted only on the top of the coping, not where the pool water meets the bottom half of the coping.

Dave Aldridge
- Butler, Pennsylvania


May 17, 2010

Well, the bacteriocides used in swimming pools are capable of etching aluminum oxide. Many cities also put fluorosilicates in their water, which is corrosive to aluminum. This is what's going to cause pitting in your aluminum oxide. If the pH of your pool water is high, this will enhance the corrosion.

Painting usually doesn't fully seal the metal, leaving microscopic points of contact for corrosion to occur. As the crevice corrosion matures, internal tensions will break up the paint, causing the corrosion to propagate.

Repainting this coping with a waterproof epoxy paint every year or two might be your best bet.

Robert H Kinner
- Toledo, Ohio, USA


May 25, 2010

Thanks again for your answer to my question and response. Could there be any association with the concrete, because the pitting is next to the concrete? There is no pitting where the coping meets the liner or water

David Aldridge
- Butler, Pennsylvania


June 22, 2011

I have the same problem. Alcoa manufactured coping for Hydra, whose parent company is PI in Tennessee. They are aware of the problem and have settled with Alcoa out of court. This of course does not help the homeowners who have the problem. My coping has been stripped and repainted twice. Still have pitting and peeling problems within weeks of repainting.

Teresa Willcutt
- Birmingham, Alabama, USA

June 23, 2011

Hi, Teresa. Thanks. Do you have a link to this suit and settlement? It strikes me as improbable that a material problem in the aluminum could render it unpaintable, as I have never heard of anything similar in my career in metal finishing. Once the coping is severely pitted, though, it might be very difficult to get it clean, rinsed, and dried in situ.

Regards,

pic of Ted Mooney Teds signature
Ted Mooney, P.E. RET
finishing.com
Brick, New Jersey

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