Corrosion in various buildings and factory piping has been a serious concern for many industries. Corrosion-related leaks or pipeline bursts may cause expensive damage to property and result in shutting down the operation. Therefore, nondestructive corrosion inspection of inside piping has become more important. Utilizing ultrasonic waves, internal corrosion and metal loss can be measured. However, existing inspection techniques were not satisfactory to determine the accurate condition. In this scenario, an automatic pipe corrosion inspection system was developed, utilizing state-of-the-art electronics technology. The system consists of an inspection device and a data processing unit. The inspection device travels on the external pipe surface, while the data processing unit displays the condition of both the internal surface and a cross section areas of the pipe. The data collected by the robot is also numerically analyzed to calculate the pipe thickness distribution, the minimum thickness, metal loss percent and corrosion rate and to estimate the remaining service life of the pipe based on proper theory. This inspection can also be applied on the threaded pipe section to determine the allowable metal loss. To verify the performance and accuracy of the data collected using the robot, partifical corroded pipes are tested. This paper will discuss the abilities and limitations of the automatic pipe corrosion inspection system and the results of the verifications tests.