An apparatus comprises an open-loop cooling system, an anode 9 at the inlet 10 of the cooling system and attached to a DC voltage supply 8. The apparatus is preferably a dry vacuum pump and may comprise at least one rotor and at least one stator 11 wherein the cooling system is provided to the at least one stator. A method for improving the corrosion resistance of the cooling system comprises flowing coolant 7 through the system such that the coolant comes into contact with at least one surface of the system and applying a DC voltage to the anode. The surface may comprise spheroidal graphite iron, grey iron or mild steel and preferably comprises spheroidal graphite iron and bright drawn mild steel. The anode preferably comprises titanium and may be a titanium-cored anode.
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