INORGANIC SALTS IN MAHOGANY SULFONATES AND THEIR EFFECT ON PETROLEUM HYDRAULIC FLUIDS

Abstract : A series of mahogany sulfonate rust inhibitors used in compounding qualified petroleum hydraulic fluids was studied in connection with the inoperability of tank hydraulic systems after short storage periods of six to nine weeks. Examination of the disassembled hydraulic components showed severe staining and rusting in valving areas having extremely critical tolerances. Analyses of the sulfonates indicated the presence of inorganic water soluble salts (calcd. as calcium chloride and calcium sulfate) ranging from 0.02 to 0.19 percent. It was found that the hydraulic fluids used in the tanks which did not perform satisfactorily contained sulfonates having a relatively high chloride salt content of 0.12 percent, while the use of hydraulic fluids with sulfonates containing less than 0.03 percent of the halide salt permitted satisfactory operation. Data are also presented which show that the concentrations of inorganic salts found in the commercial mahogany sulfonates studied do not appear to significantly affect the rust prevention properties of the sulfonates but their presence does promote corrosion due to galvanic action. A correlation was established between laboratory galvanic corrosion tests and performance tests in tank and mock-up systems.