A wear resistant coating is applied on an elbow or S-bend by weld beads applied along a pipe. A rectangular support rod is attached inside the pipe by connectors so that wheels of the carriage are guided on the corners to maintain a fixed orientation relative to the support rod. A three axis robot arm carries an electric welding head so as to be able to dynamically adjust the head both angularly and radially. A welding wire is pulled to the head by a feeding system on the carriage. The weld parameters including a predetermined wire stick out and angle of wire attack are controlled. A drive motor carried by a drive carriage propels the drive carriage longitudinally along the support rod with a series of intermediate carriages.