Macro wrote:the aluminum of your panels is not in contact with your gutter? I do not really see how there could be galvanic corrosion with rainwater which is moreover very little conductive… Moreover I think that the flow of water of your gutter would be more impacted than the downpipe….
Not at all in direct contact and they are under glass and attached to I would say 99%!
So little contact but with heavy rain with a continuous stream of water there is a "contact" ... but yes the rain water normally does not conduct well so it remains mysterious for me ... Mystery 1
Could the bottom zinc plates contain some lead?
Macro wrote:I must ask my nephew about this…. He is not a chemist but a roofer ... His specialty is listed buildings ... Well, he must not see a lot of aluminum on this kind of roofs….
Ah yes great, show him the photos of my pierced gutter ... also tell him that the horizontal part presents no problem (Mystery 2) ...
Suddenly I wonder if Ahmed's 1st hypothesis was not the right one ... some dirt in the gutter whose decomposition would have attacked the zinc (it is nevertheless punctured a little before this bend on a completely vertical part or nothing can stagnate ... Mystery 3!)?
I understand better bistro zinc than gutter jcrois !!