The Roof Cleaning Institute Of America Training & Certification Forum
"Find A Certified Roof Cleaner Directory"

Wanted to post this in the private forum. In January I was in Tampa picking up pieces of my reclaim unit from Ameritech. They stock a chemical, Hydrofloric Acid which I have found works WONDERS on rust stains, even diluted to 5%.

This stuff can't be shipped and is some pretty bad stuff, but if you can find in you area it works great.

In the photos below I softwashed the shed with a 5% SH mixture, then applied the hydrofloric @ 10% with a pump up sprayer. The results were instant, then rinsed with garden hose.

Have not tried it on shingles yet.