An ink jet printhead has improved resistance to the corrosive effects of ink by coating the surface of a photo-imageable polymer with an ink resistant film. In one described embodiment, a thermal ink jet element is formed by bonding together a channel plate and a heater plate. Resistors and electrical connections are formed in the heater plate. A polyimide layer is formed so as to overlie the heater plate to protect the electrical elements while providing pit structure for the heater and for ink flow bypass. A tantalum film is formed on the surface of the polyimide layer to protect the layer from the effects of corrosive ink. In another embodiment, the ink resistant film is amorphous carbon or silicon nitride.