Iridium-192

It is very difficult to weld or mold a solid object that has no risk of breaking in service, so testing at manufacture and during use is often essential.  Even the best welders (and welding machines) do not make 100% perfect welds. Some typical weld defects that need to be found and repaired are lack of fusion of the weld to the metal and porous bubbles inside the weld, both of which could cause a structure to break or a pipeline to rupture.

• underground pipelines are subject to corrosion and stress corrosion cracking
• pipes in industrial plants may be subject to erosion and corrosion from the products they carry