A trial of quantitative estimation of Al-corrosion detected by neutron radiography.
Comparing the hydrogen content in aluminum hydroxides, one of the main components of Al-corrosion, with that in polyethylene sheets, corroded degree of practical Al-corrosions were estimated quantitatively by neutron radiography.
Neutron Radiography of Aluminium Alloy Corrosion Damage
The potential for neutron radiography to detect hydrogenous corrosion products in aircraft structures was examined using a series of naturally and artificially corroded aluminium alloy samples. The sensitivity of this technique for detecting corrosion damage was intially assessed using the Moata reactor facility and commercial neutron radiography services. Neutron radiographs of the corroded samples were obtained using a portable accelerator and a californium-252 isotope source. Reactor, accelerator and isotope neutron radiographs have been compared to assess the sensitivity of portable neutron sources.
Neutron Radiographic Nondestructive Evaluation of Aerospace Structures
Neutron radiography with source intensities which are moderate relative to those of reactor neutron sources was found to be effective for nondestructive inspection of a variety of aerospace structures. By using either 2 mg of the isotope californium-252, or a 3-MeV Van de Graaff accelerator as neutron source, the technique was found particularly suited to evaluation of adhesive bonds in metal honeycomb and phenolic fiberglas-to-metal structures. Adhesive flaws in a variety of bonded assemblies, including a set of test panels with built-in adhesive voids and unbonds, were detected by neutron radiographic inspection. In addition, detection of corrosion hidden within metal aircraft assemblies appears to be a promising application of neuron radiography. Corrosion products introduced into one such structure in the laboratory to simulate corrosion from a field situation were radiographically imaged for sizes ranging down to 0.030 in. in diameter and 0.002 in. in thickness. It is expected that with continued improvements in imaging techniques and mobility of neutron sources for radiography the technique will gain widespread usage for routine nondestructive inspection of many types of structures.