A 12.7 mm (0.5 in.) diam tube was removed from a potable water supply due to leaks. The tube wall thickness was 0.711 mm (0.028 in.) with a thin layer of chromium plate on the OD surface. The tube had been in service for approximately 33 years. Investigation (visual inspection, EDS deposit analysis, metallurgical examination, and unetched magnified images) supported the conclusion that failure occurred due to porous material typical of plug-type dezincification initiating from the inside surface. Where the dezincification had progressed through the tube wall, the chromium plate had exfoliated from the base material and cracked. Recommendations included replacing the piping with a more corrosion-resistant material such as red brass (UNS C23000), inhibited Admiralty brass (UNS C44300), or arsenical aluminum brass (UNS C68700).

Inhibited admiralty brass (UNS C44300) condenser tubes used in a natural-gas-fired cogeneration plant failed during testing. Two samples, one from a leaking tube and the other from an on leaking tube, were examined. Chemical analyses were conducted on the tubes and corrosion deposits. Stress-corrosion cracking was shown to have caused the failure. The most probable corrosive was ammonia or an ammonium compound in the presence of oxygen and water. All of the tubes were replaced.

This article addresses the forms of corrosion that contribute directly to the failure of metal parts or that render them susceptible to failure by some other mechanism. It describes the mechanisms of corrosive attack for specific forms of corrosion such as galvanic corrosion, uniform corrosion, pitting and crevice corrosion, intergranular corrosion, and velocity-affected corrosion. The article contains a table that lists combinations of alloys and environments subjected to selective leaching and the elements removed by leaching.