DETECTION OF CORROSION ON AIRCRAFT COMPONENTS BY NEUTRON RADIOGRAPHY

Aluminium components and structures of aircrafts are susceptible to various types of corrosion due to aging, frequent changes of environment and moisture. Most of the corrosion types occurring on or in aluminium structures of aircraft contain hydrogen. Therefore, neutron radiography provides a very sensitive and informative imaging method for the detection and the investigation of corrosion attack. In support to preparations for a systematic study using both thermal and subtherma! neutron radiography for imaging of corrosion on or in aluminium aircraft components and structures, an investigation was performed in order to study some of the detection capabilities of subthermal neutron radiography. Typical aircraft structures and components with various types of natural and artificial corrosion have been investigated with the subthermal neutron radiography facility at the High Flux Reactor (HFR) Petten. The sensitivity of hydrogen detection in metal was demonstrated by microdensitometric evaluation of neutron radiographs taken from zircalloy tubes with different hydrogen loadings of the inner wall. Subthermal neutron radiography was selected due to its higher imaging potential. This potential originates from the higher linear attenuation coefficients of hydrogen for subthermal neutrons in comparison to thermal neutrons. This contribution highlights the result of the investigation on the basis of some selected examples from the study and gives an outline of the anticipated programme for a systematic study