Brass Plumbing Failure Analysis Stress Corrosion Cracking (SCC)

California failure analysis expert witness has analyzed numerous plumbing failures involving yellow brass (i.e. brass with more than 30% Zn in the alloy). The two major brass failure modes in yellow brass are dezincification and stress corrosion cracking. Above are two samples of stress corrosion cracking. Sress corrosion of yellow brass commonly involves the presence of ammonia along with the presence of stress. Upper left is a photo of a brass ferrule that cracked. The stress came from the clamping force of the ferrule on the rubber hose. These ferrules were covered with an expanded foam insulation that was painted with latex paint. At a minimum the latex paint contained ammonia; it is also believed that there was residual ammonia in the rubber foam insulation. Upper right is a failed flexible bathroom water supply line. The stress in this pipe failure is residual stress from non-uniform bending. It is believed that the ammonia came from houshold cleaners used on the plumbing. In both cases, the cracking is inter granular cracking and is attributed to stress corrosion cracking.