Ammonia is one of the few substances to give intergranular cracking on copper and brass. But how did ammonia get in contact with the tubing? Ammonia was not involved in manufacturing or installation. I scratched my head a good bit and came up with two possibilities that could have occurred during storage. One was that the droppings from birds in warehouse rafters fell on the pipe. The other was that passing dogs decorated the piping with their urine, as dogs are wont to do. In either case, the damage was done before the piping was installed. The explanation seems far-fetched and I even got a call from a member of my client’s staff asking if I were serious. I assured him I was.
The heat exchanger tubing actually suffered an attack by an old malady. Ammonia-induced cracking of copper and brass was observed in the early days of the automobile in America when farmers would store their prized horseless carriages in their barns for the winter. Often in the spring, the once-gleaming brass headlights were marred by a network of cracks, a phenomenon that came to be known as “season cracking.” The barns contained animal manure that gives off ammonia, which in turn attacked the grain boundaries. I recently learned the same term was used in India to describe cracking in brass cartridge cases that occurred during the monsoon season. Rotting vegetation produced ammonia. The cracked cases rendered the cartridges useless as ammunition.
So writes Ken Russell, MIT professor emeritus of Metallurgy and Nuclear Engineering, in “The Case of the Oleaginous Inlet“