Case Histories » Insurance

Microbial Influenced Corrosion of Copper Piping

MIC corrosion perforations in a 1-inch copper sprinkler pipe
Longitudinal cross-section through copper pipe showing 2 corrosion sites covered by “mounds” of bright green-colored corrosion products. Note: Black-colored coating on the inside wall of the copper pipe


1.0-inch OD copper sprinkler line piping.




Sprinkler line, containing stagnant water. Water was untreated with no corrosion inhibitors or biocides.


After installation, the lines were filled and left wet, with primarily stagnant conditions. Pinhole leaks were discovered at multiple locations on multiple floors.

Service Life

The sprinkler line copper piping had been in service for approximately 14 years.


Through optical and scanning electron microscopy, it was discovered that the copper sprinkler piping had failed prematurely from microbial influenced corrosion (MIC). Strong evidence was found, including regions of biofilm, large crystals of Cu2O and the base of corrosion pits, micro, bore-like holes adjacent to corrosion pits. The random nature of the pitting indicates failure due to MIC.