Studies on Rust Inhibitors. III.

Abstract

With a view to studying the effects of the polar groups of rust inhibitors upon the results of different corrosion tests, we took up in the last installment of this series organic amine soaps and orthophosphate esters as the inhibitors, and using the rust-preventive oils prepared with these inhibitors added to lubricating oils, carried out seven sorts of corrosion tests and measured displacement energies in the interfaces between steel and oil and water.For the preparation of organic amine soaps, six kinds of amines, i.e. coconut amine, oleyl amine, oleyl imidazoline, aminopropyl tallow amine, condensed composition of oleic acid and diethylene triamine, and rosine amine were employed.The orthophosphate esters used in the test included those three kinds of esters, i.e. mono, di, and mixed ester which were prepared by the reaction of oleyl and phosphorous pentoxide, and neutralized salts of orthophosphate esters with coconut amine were also prepared for the test.It was found that organic amine soaps indicated as the special property of that type much better results in the sulfuric acid immersion test than any other type of rust inhibitors did; whereas in the heat stability test and the non-ferrous metal immersion test they were not proved to be effective. It must be noticed too that the discoloration of oil is frequently found on the surface of metal while the metal is in storage with this type of inhibitors applied thereon. It was found further that oleic amine soaps, such as coconut amine, oleyl amine and rosine amine, which are simple in structure, did not yield good results in the humidity cabinet test, the reaction test by potassium ferricyanide and the salt water immersion test as compared with the remaining three, and that they were inferior in their water displacement quality.As for orthophosphate esters, the anti-corrosion properties of this type of inhibitors were indicated with fairly good effect in the humidity cabinet test and the reaction test by potassium ferricyanide, and their water displacement energies showed minus values. In the salt water immersion test also they yielded rather good results. In the sulfuric acid immersion test, the heat stability test and the non-ferrous metal immersion test, however, they showed very poor results. One of the main defects of amine phosphates is, it is to be understood, that they are prone to cause corrosion during the storage period of steel plates.