Corrosion Of Mechanical Joint Bolts

The mechanical joint has been in use since 1927 and the corrosion of mechanical joint bolts has been the subject of many studies. Most studies searched for ways to prevent the bolts from failing prior to the pipe. It was found that in corrosive soils, the bolts were the most vulnerable component of the system. In many cases, the bolts failed due to corrosion, long before the pipe became unserviceable.

In cast-iron pipe, the products of corrosion remain in place and exhibit enough strength, coupled with the surrounding metal, to withstand considerable pressure without failure. This phenomenon has been repeatedly demonstrated by the Cast-Iron Pipe Research Association (CIPRA), the predecessor of the Ductile-Iron Pipe Research Association (DIPRA). This phenomenon was also reported by the National Bureau of Standards in a paper by Melvin Romanoff in the September 1964 issue of the "Journal of the American Water Works Association." Some pipes held as much as 500 psi even with complete perforation of the pipe wall by graphitic corrosion. However, even though the pipe could have remained serviceable in this condition, if the joint leaked due to bolts that had corroded, the pipeline had to be repaired.

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•Article: Corrosion Of Mechanical Joint Bolts