Published on August 29th, 2012 | by Henri


Rusty metal chimney stains roof

Q.    Even though we applied a galvanized spray paint coating on the metal chimney of our boiler some time ago, we are still encountering a rust-colored stain on our now newly roofed motel. First, what would be the cause of this rust but most important, how can we remove this rust-looking streak area from our new light grey shingles?

I read your column and blog a lot; thanks for all of the of good input.

A.    If you have thoroughly coated the exterior of the metal chimney with a paint formulated for galvanized metal and there was no loose rust on the chimney before you painted it, the rust streak may actually be an oil deposit from a poorly adjusted boiler burner. Do you have the burner serviced every year by a competent technician?

On the other hand, if there was some loose rust on the exterior of the chimney, that may cause the paint not to stick.

It may be quite difficult to remove either rust or oil stains from asphalt shingles. Do not use any product with a petroleum base as it would damage the shingles irreparably. Try a solution of one cup TSP-PF to one gallon of water. Apply it with a paintbrush but do not scrub or rub as it would dislodge the mineral granules that protect the asphalt from the destructive rays of the sun.

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