Corrosion, including stress corrosion cracking (SCC), constitutes about 12% of the failures of gas transmission lines. Two types of SCC have been observed: intergranular SCC (IGSCC) under alkaline conditions and transgranular SCC (TGSCC) under near-neutral conditions. The environmental and electrochemical conditions under which these types of SCC can be produced in the laboratory have been reasonably well established. However, a quantitative relationship between the laboratory environments in which SCC can be reproducibly observed and the chemistry of trapped water under disbonded coatings has not been established. The purpose of this paper is to review the state of knowledge of the environmental conditions leading to either type of SCC and relate this to the evolution of the actual environment under disbonded coating. The relationship between SCC and chemistry of trapped water is examined through the use of a comprehensive thermodynamic model. The temporal and spatial evolution of the trapped water chemistry is examined as a function of external conditions through the use of a reactive-transport model.