Plural snap-acting, pressure-responsive, metal diaphragms having dished portions which permit the diaphragms to move from one dished configuration to an inverted dished configuration with snap action are disposed in nested relation to each other in a pressure switch. When fluid pressures are applied to the nested diaphragms from one side thereof, the diaphragms retain their original dished configuration during variation of said fluid pressures over a selected pressure range. However, the diaphragms move together with snap action to their inverted dished configuration when said fluid pressures reach predetermined levels. The diaphragms have protective oxide surface coatings which prevent galling of one diaphragm by another during said snap-acting movement of the nested diaphragms whereby the diaphragms retain their pressure response characteristics over a long service life.