An exhaust treatment assembly for receiving exhaust gas from a motor vehicle includes a mix pipe, a sheath, and a heater. The mix pipe at least partially defines a passage adapted to receive the exhaust gas and a chemical reductant. The sheath includes a first end fluidly sealed to the mix pipe. At least a portion of the sheath is radially spaced apart from the mix pipe to at least partially define a gap. The heater is disposed in the gap. The heater is adapted to heat a reductant impingement surface.