Gray-colored corrosion patina on a copper water supply line under a sink in a home with Chinese-made drywall.
Copper tubing blackened by sulfur-caused corrosion, easily rubs off when touched.
Plumbing pipe blackened by high sulfur content in Chinese made drywall installed in a home.
On the left a copper tube after being exposed to normal drywall. On the right a black, corroded copper tube after being exposed to problem drywall.
A black, corroded toilet water line.