Coupling media preparation refers to the collection of actions and processes used to ensure that the medium used to aid transmission of ultrasound energy from a generating machine to a metal surface is adequate. The preparation is performed for the purposes of corrosion testing.
A coupling media preparation may also be known as a couplant.
Coupling media must be evaluated to ensure minimum interference with the energy it transmits. It must not absorb, react with, redirect or diminish the energy. Coupling media are fluids such as water, oils, creams or gels.
Ultrasonic testing is a procedure used to examine metal surfaces for corrosion, such as when testing for corrosion under insulation (CUI). The testing requires the transmission of ultrasound energy to the metal's surface via a coupling medium. For corrosion-related applications, it is best to avoid the use of water as a medium because it generates an electrochemical cell with free ions that could ultimately increase the corrosion rate. Ultrasonic testing is ideal for metals located under layers of insulation because it does not require access to the entirety of the surface being tested.