Not all metals get along!
Metal roof corrosion happens. This idea may be foreign to us guys who don’t recall chemistry class in school, but it is necessary to understand similar vs. dissimilar metals when roofing. Anytime you are selecting metals that are in direct (touching) or indirect (runoff) contact with one another, you should have referenced the “Electrochemical Series” chart. If you have ever heard the term “galvanic corrosion”, this is what it is referring to. When an electrolyte (moisture) is in the presence of two metals, the less noble metal will experience accelerated corrosion. The Electrochemical Series is a chart that orders metals from the least noble (anodic) to the most noble (cathodic). Therefore, the further apart the metals on the chart, the faster/more aggressive corrosion will be.
1) Copper and Stainless Steel – Since these metals are next to one another on the chart, they are compatible and therefore commonly paired together for roofing purposes.
2) Zinc and Copper – Never pair these two metals together for installation. They’re separated on the chart and galvanic corrosion will show quickly. Be careful of copper runoff from plumbing pipes that may leak onto zinc roofing material.
With a little bit of advance planning, you can prevent metal roof corrosion. Don’t forget to reference this chart to make sure you don’t run into this ugly and destructive problem.