Stains on Galvalume roof

I have an 8 year old unpainted galvalume standing seam roof. It was getting dingy so I had a roof cleaner clean it with 3% sodium hypochorite wash. Several panels now have a very dark stain that does not appear to be rust (see photo). Any idea what this is or how to get rid of it? Thanks for input.		Guest User 9/14/2017	Share Or copy this URL: https://www.metalroofing.com/spirit/comment/22434/find/
Who is the panel or coil manufacturer? Did you consult with them on what an approved roof wash was?		Eric Novotny An informed customer is the Best Customer! 9/14/2017	Share Or copy this URL: https://www.metalroofing.com/spirit/comment/22435/find/
Thanks for getting back Eric. Guarantee papers say Baldwin Steel Company but the only vendor I could find on the web with that name does not manufacture Galvalume roofing. Everything we read said that weak sodium hypochlorite solution or dish detergent was the way to go. The remaining 2000 sq. ft. of roof came out beautifully except these few panels. Do you know of any manufacturers that would be familiar with the chemistry of Galvalume? There has obviously been a chemical reaction to something in that one spot which is not impacted by trees or anything overhead except sky.		Guest User 9/14/2017	Share Or copy this URL: https://www.metalroofing.com/spirit/comment/22436/find/
Are you sure the reaction is in the panel finish? Is it possible that there is a thin layer of biological matter on that panel that was reactive with the wash?		Eric Novotny An informed customer is the Best Customer! 9/14/2017	Share Or copy this URL: https://www.metalroofing.com/spirit/comment/22437/find/

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