Synthesis And Properties Of Carboxylic Acid Modified Bifunctional Additives For Water-based Hydraulic Fluids

Traditional water-based hydraulic fluids are usually compounded with sodium nitrite rust inhibitor and oleic acid soap and castor oil soap lubricant which has problems of toxicity and stability.Existing carboxylic acid additives have weak anti-rust and lubricating properties due to few adsorption sites.In order to improve the overall performance of hydraulic fluids and promote product upgrading,it is urgent to develop a dual-function additive.Under the conditions of n(boric acid):n(diethanolamine)of 1:2.25,reaction temperature of 110°C,and reaction time of 1 h,the intermediate boric acid diethanolamine was prepared by esterification.Under the conditions of n(intermediate):n(carboxylic acid)is 1.2～1.5,the reaction temperature is 120～160℃,and the reaction time is 3～5h,capric acid,lauric acid,oleic acid and ricinoleic acid are prepared by acylation reaction.BM-1,BM-2,BM-3,BM-1 four additives.The data by FT-IR and ~1HNMR indicated that B-O and amide groups were successfully introduced into the carboxylic acid structure.The antirust properties of additives on HT300 gray cast iron in 330mg/L Na Cl corrosive medium were studied by methods such as corrosion weight loss,electrochemistry and quantum chemistry.Lubrication properties of additive aqueous solutions were investigated by four-ball friction experiments.The antirust mechanism and lubricating mechanism of additives were discussed.The research results show that when the additive with a mass concentration of 0.5%is added,the HT300 gray cast iron soaked in the corrosive solution of the four additives has no rust and discoloration.Electrochemically indicated that the additive is an anodic rust inhibitor,which inhibits the transfer process of charge between the graphite electrode and gray cast iron.The adsorption of additive molecules on the surface of HT300 gray cast iron satisfies the Langmuir isotherm adsorption model,which is a spontaneous physical and chemical adsorption process.The additive forms an adsorption film through the physical adsorption of N~+ions,the coordination bond formed by O atom and amide group filling the 3d orbital of Fe with electrons,and the feedback bond formed by the terminal N atom accepting the electron lost from the 1s orbital to form an adsorption film,which hinders the Cl~-ion erosion.When adding additives with a mass concentration of 0.5%,the PB values of the aqueous solutions of the four additives are all>392N.With the increase of the concentration,the diameter of the wear scar first gradually decreased and then tended to be flat.With the increase of the load,the diameter of the wear scar first increased,then decreased and then increased.Additive molecules mainly play a lubricating role through the adsorption film when the load is low.As the load increases,the B penetrated into the surface of the steel ball participates in the tribochemistry to form a high-strength chemical reaction film,which works together with the adsorption film to lubricate the steel ball.