Alternatively referred to as CD bronzing, bronzing is corrosion similar to CD rot caused by a manufacturing defect. When bronzing occurs the top or bottom of the disc changes colors often changing from a silver color to a bronze, brown, yellow, or gold tint. Over time, this change causes the CD to stop working. The company largely responsible for this defect was PDO (Philips & DuPont Optical) in Lancashire, United Kingdom with discs manufactured between 1988 and 1993.
Because this is a manufacturing defect, no matter how the disc is handled if it's defective it will eventually become bad. However, as mentioned above this issue only affected discs manufactured in the late 80's and early 90's by PDO.