Preventing green corrosion on textured thin sheet brass
I bought a gorgeous new-but-antique looking wall mirror a few years ago. Planning to redecorate, it waited in the basement in its shipping carton. I was finally ready for it today and brought it upstairs ready to hang it only to find that it had corroded in the interim.
It had splotches of crusty green blue in numerous places. This mirror (which is quite large at 22" x 26") is made of thin brass with an elaborate texture stamped into it, which is then formed around an openwork wooden framework and nailed in place with tiny nails. I decided to clean it up with Penny Brite, which is what I normally use for tarnished brass or copper. This turned into a 6 hour marathon. Because of the underlying wooden framework I had to make sure it did not get too wet. The corrosion was very resistant: I had to use alternately cleaner and scotchbrite. Some parts stayed a dark spotty brown or red even after intense scrubbing, but at last all the green was gone. It originally had a nice patina in the low parts: not anymore. I finally got it 90% clear and dried it off. I reapplied the patina (another hourÂs work) and repolished those parts.
But as soon as it was dry I saw the green corrosion blooming up again! The worst areas are where the brass meets the mirror surface at a right angle, and on the sides. This surface is not textured but smooth. I canÂt possibly scrub this more than I already did. This area also I made dark brown with the new patina; corrosion coming right through it (from what I can tell).
I want to seal it to eliminate the corrosion spreading, and maybe paint over these sides with dark brown paint. At least the most important part, the textured surface seems to be OK. I donÂt want to lacquer it, it would be too difficult to remove if the corrosion canÂt be stopped and I have to clean it periodically. If I paint over the corrosion with acrylic or oil paint will that stop it from spreading? I was planning on using paste wax to seal the brass instead of lacquer. Will using paint and the paste wax work? I remember reading somewhere about using brown colored shoe polish on brass. What would work best?