I was in a Chinese drywall house today, before any rehab was done. The pictures are on my FTP site, (use your back button to get back to index) http://gfretwell.com/ftp/Chinese%20Drywall/ I will make up some HTML when I get a chance but these are the pictures if you want to browse.
Basically anything covered was OK (including under screws). Brass and copper was affected, steel and aluminum didn't seem to be. You could get the black stuff off the wire with your fingernail. Note the bus bars and lugs in the panel look brand new. (aluminum alloy)
Plumbing fixtures took a hit as did a set of brass keys hanging on the wall.
This house was abandoned at final trim and sat empty for well over a year.
I wonder what kind of condition the AC evap coil is in. Iíve heard there has been a lot of issues with formicary corrosion and pin hole leaks occurring in them because of the off gassing from that crappy Chinese drywall. Iím betting the corrosion would have been a lot worse at the sink faucets and drains if water had been contacting the metal daily from use by occupants.
I assume the gypsum in this sheetrock has an excess of sulfuric acid in it - much gypsum plaster is now made at the top of coal-fired power station chimneys by converting the sulfur pollutants into acid, then 'killing' with limestone. Full of uranium too, from the coal. Try a geiger counter next visit Greg!
Yep John, that is the problem. China used fly ash from coal plants to make the drywall, as some US plants do, but their coal is a lot dirtier and the sulfur in the coal creates a SO2 out gassing from the drywall. It is still not clear how long it takes for it all to come out but during the time it does it eats anything copper. I do think, eventually it would reach a safe level but by then it is too late. nobody is going to take a chance on it.