Study On Flow-Induced Corrosion Of Typical Metal Materials In New Coolant

In the liquid-cooled circulation system,ethylene glycol water-based coolant is one of the most widely used coolants.In liquid cooling systems,aluminum and its alloys,copper and its alloys are widely used because of their good physical properties.Prolonged high temperature operation will cause acidification of glycol,which will aggravate the flow-induced corrosion of metal materials and seriously affect the normal operation of liquid cooling systems.Therefore,it is of great significance to study the flow-induced corrosion behavior of typical metal materials in the coolant.In this paper,the flow device is used to study the flow-induced corrosion behavior of typical metal materials(brass,copper,5A02 aluminum and 5A06 aluminum)in a new coolant by weight loss test.On this basis,the electrochemical monitoring technology is used to study the polarization behavior of typical metals in the flow state and the coupling sensitivity of 5A06 and dissimilar metals.Then explore the effect of corrosion inhibitor on galvanic corrosion.The surface potential and morphology of rust-proof aluminum welded parts in a new coolant were studied by using surface analysis and testing technology.Through the durability experiment,the long term flow conditions,the typical metal durable corrosion behavior and coolant performance changes.Finally,the synergetic mechanism between hydrodynamic action and electrochemical corrosion is revealed.The results of the study indicate that the interaction between the hydrodynamic process and electrochemical corrosion causes the flow-induced corrosion rate of the four metals to increase when the flow velocity increases.The addition of corrosion inhibitors can weaken the flow-induced corrosion.The corrosion rates of the four metals after the addition of corrosion inhibitors meet the relevant technical requirements(technical requirements are less than 1.5 g·m-2·d-1).The coupling sensitivity of 5A06 to copper and 5A06 to brass is grade E,and the coupling sensitivity of 5A06 to carbon steel is grade D.Both require protective treatment of the material surface before direct contact.In the glycol-based coolant containing corrosion inhibitors,the cathode process in the anti-rust aluminum corrosion is oxygen diffusion control,and the anode process is the metal passivation process.The corrosion inhibitor is attached to the metal surface to form a film,which promotes the reduction of the current density in the anode process and increases the resistance of the anode process.This indicates that the corrosion inhibitor is an anode type corrosion inhibitor.And as the flow velocity increases,the polarization resistance decreases,and the flow-induced corrosion of 5A02 and 5A06 increases.The welding process will affect the corrosion tendency of the rust-proof aluminum.The surface potential of the base material,heat affected zone and weld of the rust-proof aluminum weldment gradually becomes negative.The self-corrosion potential at the weld is lower than that of the metal base material.The polarization resistance at the weld is smaller than the base material.The corrosion tendency of the weld is greater,which is the weak part in use.The durability flow-induced corrosion rate of aluminum alloy and its welded parts all meet the relevant technical requirements.The self-corrosion potential at the inner wall of the pipe elbow is more negative.In engineering applications,attention should be paid to corrosion and protection at the inner wall of the pipe elbow.The new coolant has good heat exchange performance,combined with changes in pH and conductivity,it is recommended to replace the new coolant in time after 1 month of continuous operation to ensure the normal operation of the equipment.