@roger,
Yeh, the sheetrock is adultered with Sulfuric acid. Gypsum can form H2SO4 and H2SO3 by bacterial decomposition if the gypsum is stored in wet, anaerobic conditions. The gypsum will dissociate and yield acid. In the US, Canada, and most of the rest of the world, gypsum is mined and carefully stored as anhydrite. I have no idea why China was doing this. All the gyp board in new construction is possibly compromised because it can dissolve the nails and any Al frames and corner moldings that the board touches.
Chinese stuff needs to be monitored more closely. I had to have brake lines replaced twice in my 03 Ford 250 =D and the replacements are all made in China. They are crap, but because of price concerns Ford motors has gone to most of its replacement parts mfd in China.
The word "toxic junk" comes to mind.