Under the front aluminum extrusion is a strip of 3M Very High Bond double sided adhesive foam tape which acts as a barrier between the aluminum and the front lip of the gutter, so the metals would have a very difficult time touching each other. Where there is a presence of water, air, and dissimilar metals, sometimes corrosion can occur. If you are still concerned, you can always apply a coating on the mill-finish aluminum. All hardware stores sell paint coating products that you can apply to a mill finish aluminum. In a majority of the installations, the stainless steel micro-mesh doesn’t come in contact with the copper gutter because it’s installed between the front and rear mill finish extrusions.