Bronzing

Also known as CD bronzing, bronzing is a corrosion that is similar to CD rot that is 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 and over time can cause the CD to stop working. The company largely responsible for this defect was Philips & DuPont Optical (PDO) in Lancashire, United Kingdom with discs manufactured between 1988 and 1993.
Because this is an actual manufacturing defect no matter how the disc is handled if it's defective it will eventually become bad. However, as mentioned above this issue widely only affected discs manufactured in the late 80's and early 90's by PDO.
Also see: CD definitions, CD rot