An ion implanter has a coating of low resistivity silicon carbide on one or more of the conductive surfaces that are exposed to ions. For example, ions are generated in an ion source chamber, and the interior surfaces of the walls are coated with low resistivity silicon carbide. Since silicon carbide is hard and resistant to sputtering, this may reduce the amount of contaminant ions that are introduced into the ion beam that is extracted from the ion source chamber. In some embodiments, the extraction electrodes are also coated with silicon carbide to reduce the contaminant ions introduced by these components.