Liquid damage refers to any signs of corrosion that may be present in a mobile phone or on a printed circuit board, component or user interfaces. In some cases, the liquid damage may not be visible to the naked eye but can be detected with the use of a professional microscope.Liquid damage causes latent damage to the circuitry, meaning that although the phone may appear to be operational, there is internal degradation to the circuitry, which may result in a failure.Click here for more information on what may cause liquid damage.