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Fire chief concerned about corrosion of aluminum ladders from stainless steel racks

We are having a problem with corrosion on our aluminum ground ladders that are stored in full length stainless steel slides in the rear of our ladder truck. The ladders were inspected by a testing company, but no mention was made of this being a problem. Our concern is not with the aesthetics, but whether or not there is any degradation of the aluminum to the point where the ladder may fail under stress. Can anyone point me in the right direction as to how I can find this out? The truck was delivered in early 2002, and I assume the ladders are not that much older than two years.

Kevin Kubala
Fire Chief - Bethel Park, Pennsylvania, USA
2003

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If you had not had the equipment inspected, I would have felt obligated to remain silent, because to reassure you about the safety of something I haven't even seen would obviously be risky. But it is quite likely that no galvanic corrosion is occurring because anodized aluminum has an insulating skin; further, if the items are dry and clean, no galvanic corrosion occurs since you need an electrolyte as well as dissimilar metals in metallic contact with each other. Also, if any galvanic corrosion were to occur it would be extremely obvious visually (basically, missing metal); finally, such corrosion does not embrittle the aluminum or change the characteristics in a way that could precipitate catastrophic failure. If the inspectors said the equipment was okay, rest easy. My son is a volunteer and I would have no reservations about him climbing your inspected ladders.

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
2003

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Ted,

Thanks for the reply. So basically, if there is no electrolyte involved, the mere fact that the aluminum ladders touch the stainless steel does not automatically cause any type of corrosion or reaction. Is there any way to determine what caused the pitting on the rails?

Kevin Kubala
Fire Chief - Bethel Park, Pennsylvania, USA
2003