Which method is typically more reliable for detecting very small surface discontinuities?

Liquid penetrant testing is highly effective for detecting very small surface discontinuities. This non-destructive testing method works by applying a liquid with high surface wetting characteristics to the surface of an item. After it has penetrated into any surface-breaking discontinuities, the excess penetrant is removed from the surface. Then, a developer is applied, which draws the penetrant out of the discontinuities and onto the surface, creating a visible indication.

This method is particularly reliable for detecting fine cracks and porosities that are open to the surface, allowing for a high degree of sensitivity to small defects. Liquid penetrant testing can reveal discontinuities that may be missed by other methods, particularly those that do not effectively interact with very small surface flaws.

Other non-destructive testing methods, such as ultrasonic testing and X-ray testing, have their own benefits but may not be as adept at capturing minute surface flaws as liquid penetrant testing is. Ultrasonic testing typically requires a certain minimum size of defect to generate a signal, making it less sensitive to very small surface discontinuities. Similarly, while magnetic particle testing is effective for ferromagnetic materials, it also may not indicate very fine surface cracks as reliably as the penetrant method. X-ray testing is excellent for