Corrosion quantification by different nondestructive inspection methods

Boeing investigated corrosion effects on crack growth rates under a USAF contract with Tinker AFB in an engineering assignment performed by the Boeing Wichita. Sixty-eight crack growth specimens were notched, corroded, and fatigue test to determine crack growth rates. After salt spray exposure and crack growth testing the specimens were nondestructively inspected (NDI) by five different NDI methods to determine the amount of material lost. The NDI methods were chosen to represent different methods that could detect the presence of corrosion and digitize the data for analysis later to determine percent material lost. The NDI methods evaluated were computed tomography, pulse-echo ultrasonic c-scan, eddy current c-scan, thermography and digital radiography. Microscopy cross sectioning was also performed to visually document the corrosion damage. This data was used to compare the effectiveness of the NDI methods for detecting and quantifying corrosion damage and was used in the reanalysis of pre-corroded crack growth data. The results of NDI portion of this study are presented.