A fluid injector includes a valve structure movable in the passageway between a first position and a second position. The valve structure includes a hollow tube having a longitudinal axis and a valve member connected to an end of the tube by a weld, with a weld zone being defined inside of the tube generally adjacent to the weld. The tube has surfaces defining a through-hole that is disposed transversely with respect to the longitudinal axis of the tube. The through-hole permits the fluid to enter an interior of the tube. Corrosion prevention structure is disposed in the tube between the through-hole and the valve member to prevent the fluid in the tube from accessing the weld zone.