A steady-state version of the surface state model of tribocharging is developed and compared to the effects of carbon black on tribocharaging of two-component developers. In this model, the rate of charging of the toner and the rate of discharging of the toner, because of increased conductivity related to the carbon content of the toner, are assumed to be equal at steady state.Carbon black was found to have the following effects on the triboelectric properties of model toners made from carbon black in a polymer binder:1. Increasing the carbon black content causes the absolute value of the charge-to-mass of model toners to decrease when the toner is charged positively or negatively using poly(methylmethacrylate) coated carrier or poly(vinylidine fluoride) coated carrier.2. The ratio of q/m when the toner is charged positively to q/m when the same toner is charged negatively is a constant.3. Increasing the carbon black content causes the absolute value of the slope and the intercept of linear plots of mass-to-charge as a function of the mass ratio of toner to carrier to increase.The model predictions agree with these observations.