Which couplant is most commonly used in immersion testing?

In immersion testing, water is the most commonly used couplant due to several important factors. First, water provides excellent acoustic coupling between the ultrasonic transducer and the test material, allowing for efficient transmission of sound waves. This ensures that the ultrasonic signals can penetrate the material effectively, which is crucial for accurate evaluation and detection of flaws.

Additionally, water is readily available, inexpensive, and non-toxic, making it an ideal choice for a variety of testing environments. Its characteristics, such as low viscosity and high density, also contribute to good signal propagation, reducing the likelihood of signal attenuation.

While other couplants like oil, glycerin, and alcohol may be used in certain specific applications, they do not have the same level of widespread application as water in immersion testing. Oil, for example, can be more viscous and may not transmit sound waves as effectively as water. Glycerin and alcohol might have limited use depending on the material being tested, but water remains the standard choice for most immersion testing scenarios.