Published: Jan 1986
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The physical processes of corrosion are examined as possible sources of acoustic emission (AE). Detectable emission is produced by film cracking, gas evolution, hydrogen-induced microcracking, plastic zone growth, and discontinuous crack movements in stress-corrosion cracking (SCC) and hydrogen-assisted cracking. By these mechanisms corrosion can be detected while it is occurring. Practical applications include rapid evaluation of the susceptibility of materials to corrosion, particularly to SCC. Apart from real-time monitoring of the corrosion process, the structural damage caused by corrosion can be detected after it has occurred by AE monitoring during application of stress. In this testing mode, emission is enhanced by surface degradation and corrosion products. Pipelines and aircraft structures have been tested in this way. In large structures it is generally more practical to detect the results of corrosion than to monitor the corrosion process itself. For success in field applications attention must be paid to issues such as background noise and wave attenuation, and operator training and experience is an important factor.
acoustics, emission, corrosion, crack propagation, nondestructive tests
Physical Acoustics Corporation, Princeton, NJ