Abstract: A flange and casing insulation testing instrument, comprising a means to apply a small voltage across a pair of insulated pipe flanges or between an insulated pipe and casing in an environment of earth and ground moisture to effect an electrolysis charging between the two components. First and second timers are provided to record the time period required to effect charging to a predetermined level to allow the establishment of a data base relating to the system being monitored. A microammeter provides an indication of the state of the insulation between the elements of the system, i.e. if the flanges or pipe and casing are shorted together, there will be no residual charge.