The cracks offered a starting point for internal corrosion, which could hasten failure.
The other common cause of explosions was internal corrosion which weakened the boiler barrel so that it could not withstand normal operating pressure.
The cause was due to severe internal corrosion of the pipeline.
Iron pipes, even though galvanized when new, may show internal corrosion, and this can produce rust as suspended matter.
Finally, rocket engines often run "rich" to slow internal corrosion.
It was the sound of incipient internal corrosion, of inner fortifications giving way.
Generally, non-repairable internal corrosion of parts results if you get the phone wet or use wet hands to push the buttons.
Ductile iron pipe is somewhat resistant to internal corrosion in potable water and less aggressive forms of sewage.
Cement mortar linings have been found to dramatically reduce internal corrosion.
But apart from internal corrosion, our promise has to meet an external challenge: that is the present worldwide disintegration of Western civilization.