Radiography is the most commonly known non-destructive test method. Radiography can be used to obtain a permanent image of the surface and sub-surface (embedded) discontinuities. The same discontinuities can be radiographed again after a period of service life and the radiographs can be compared to measure the change in the size and shape of the discontinuity. There are numerous applications of radiography in engineering applications.
Some of the common uses are the detection of surface and subsurface features of interest in welded parts, castings, forgings, wall thickness measurement, corrosion mapping, detection of blockages inside sealed equipment, detection of reinforcing the material in concrete slabs, measuring bulk density of materials, measuring porosity in concrete, etc. The conventional film radiography is the most sensitive test method.