Abstract: A method and apparatus for metal degreasing or metal phosphatizing that utilizes a low boiling point solvent. The apparatus comprises a vessel defining a reservoir of solvent and a zone of solvent vapor above the reservoir, and an external heat pump system having a heat-emitting section and a heat-absorbing section to provide the necessary heating and cooling for the vessel. Intermediate heat transfer fluid loops transmit heat between the vessel and the heat pump, and include reservoirs to inhibit the loss of thermal balance in the heat pump. Coolant fluid is circulated through the solvent reservoir to inhibit solvent evaporation when the apparatus is not being used.