Or copy this URL:
https://www.metalroofing.com/spirit/comment/11887/find/
You may be able to cleanse it with a mixture of water, detergent, and TSP.
At one time there was a coating out which purported to fix oxidized surfaces but they seem to be out of business. Perhaps it did not work so well.
8/9/2008
Isaiah Industries, Inc.
8/26/2008