In order to study the relationship between rust preventive additives and their bases, mainly of corrosion preventives of solvent cut back type, four sorts of corrosion tests were carried out.Rust preventive properties were so remarkably improved as the bases were shifted from lubricating oil alone to petrolatum blended with lubricating oil and solvent, then further to petrolatum mixed with solvent that testing terms had to be put off according to the alternation of the bases mentioned above.When rust preventive additives were used to each of the bases, sorbitan mono oleates and barium sulphonates were superior to remaining three additives in the salt spray test, and oleyl sarcosine showed good results in the humidity cabinet test with sulphure dioxide employed. But in the accelerated weathering test and the outdoor exposure test they did not yield good results. In addition, especially when lubricating oil alone was used as a base, corrosion occured so easily that the effects of additives used couldnot be evaluated well.On the other hand, by the use of a rust preventive oil of P-1 type, in which, different from three kinds of bases already mentioned, asphalt mixed with solvent is used as a base, corrosion was unlikely to occur in the accelerated weathering test as well as in the outdoor exposure test even though the additives were not used.