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"Aluminium Roofing Strips with Copper Nails - Corrosion"

July 18, 2016

Q. I live on the sea front in an old Victorian house. Last week I had my slate roof repaired with the new slates retained with aluminium strips secured with.... copper nails.

I've just read with some concern about galvanic corrosion between these two metals and I now realise the aluminium strips are likely to corrode over time. The point they are nailed is actually under the slates so it should be dry most of the time, but occasionally the winter gales will drive water under the slates and it will be brackish because of the sea. There's also the possibility of capillary action to consider.

My question is how fast is this process? How long are the strips of aluminium likely to last before they turn to powder due to their interaction with the copper nails and my new slates start falling out! Should I worry?

Mark Jones
Home Owner - North Wales - United Kingdom

July 2016

A. Hi Mark. Presumably the nails are rather small compared to the size of the aluminum strips, in which case the amount of galvanic corrosion current they can drive is quite limited. Since appearance is not an issue, with the aluminum being covered, I doubt that it's anything to worry about.


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Ted Mooney, P.E. RET
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