Abstract: A gas sensor has a sensor element, a main metal fitting and a buffer fitting made of metal materials. The sensor element has a solid electrolyte body of a cylindrical shape, an outer electrode formed on at least an outer peripheral surface of the solid electrolyte body and a front end side surface of the projecting part, and a porous ceramic layer formed on the front end side surface of the projecting part. The main metal fitting has an insert hole through which the sensor element is inserted and a stair-shaped part projects inwardly from an inner peripheral surface of the insert hole toward a radial direction of the main metal fitting. The buffer fitting is arranged between the porous ceramic layer and the stair-shaped part, and the metal materials which form the buffer fitting have a depassivation pH value of less than 1.0.

Abstract: A gas sensor has a sensor element, a main metal fitting and a buffer fitting made of metal materials. The sensor element has a solid electrolyte body of a cylindrical shape, an outer electrode formed on at least an outer peripheral surface of the solid electrolyte body and a front end side surface of the projecting part, and a porous ceramic layer formed on the front end side surface of the projecting part. The main metal fitting has an insert hole through which the sensor element is inserted and a stair-shaped part projects inwardly from an inner peripheral surface of the insert hole toward a radial direction of the main metal fitting. The buffer fitting is arranged between the porous ceramic layer and the stair-shaped part, and the metal materials which form the buffer fitting have a depassivation pH value of less than 1.0.