Cavitation Corrosion Of Cast Aluminum Alloy In A New Coolant

Cavitation erosion will seriously affect the normal operation of the electronic liquid cooling system.In this paper,the cavitation corrosion behaviors of cast aluminum alloy in a new coolant were studied by weight loss method using a cavitation erosion instrument.At the same time,the corrosion electrochemical kinetics of cast aluminum alloy in the new coolant under cavitation was illustrated by electrochemical corrosion techniques.Finally,using the modern surface analysis technology,the formation and damaged mechanism of surface film of cast aluminum alloy in the new coolant under cavitation were studied.With a modern surface analysis technique,the synergistic mechanism between electrochemical corrosion and cavitation was researched.It was found that,the synergistic effect between electrochemical corrosion and cavitation resulted in the increment of the cumulative weight loss of cast aluminum alloy in the new coolant with cavitation time.The cavitation corrosion rate of the cast aluminum alloy increased first,and then decreased with cavitation time.The addition of inhibitor retarded the cavitation corrosion of cast aluminum alloy,however,it did not completely retard the occurrence of corrosion.Therefore,the synergistic effect between electrochemical factors and cavitation still speeded up the cavitation corrosion of cast aluminum alloy.Although cavitation enhanced the cathodic oxygen diffusion process,it promoted the passivation of cast aluminum alloy.Therefore,the corrosion process was dominated by anodic process control.When the anodic type inhibitor was added,the electrochemical corrosion of the cast aluminum alloy was effectively ratarded,showing that inhibitor could decrease the synergistic effect between the electrochemical corrosion and the cavitation.Finally,cavitation corrosion of the cast aluminum alloy was retarded.In the coolant without inhibitor,cavitation damaged the oxide film on the surface of cast aluminum alloy,forming pits and holes.Under cavitation,the electrochemical impedance spectroscopy had two time constants,and that there was an inductive at a low frequency region.The Rct decreased with cavitation time,indicating that cavitation accelerated electrochemical corrosion process.When the corrosion inhibitor was added,the electrochemical impedance spectroscopy was a deformed semi-circle with two time constants.However,under cavitation,the electrochemical impedance spectroscopy was composed of a capacitive resistance arc at a high frequency resion,and an inductive arc at a middle frequency resion,and capacitive reactance arc at low frequency.In this case,EIS had three time constant.Showing that,cavitation corrosion complicated mechanism would be very.In the coolant without inhibitor,the compositions of the surface film on the cast aluminum alloy were mainly AlOOH,silicon oxide,and silicate.Once cast aluminum alloy was subjected cavitation,silicon oxides and silicates gradually pelled off,forming pits and holes on the surface.During the time,cavitation promoted the formation of AlOOH and Al2O3.The addition of inhibitor accelerated the formation of AlOOH and Al2O3 on the surface of cast aluminum alloy,in this case,the film was a mixed inhibition film with nitrogen and phosphorus elements,and that this film inhibited the formation of pits,holes,and cracks on the surface of cast aluminum alloy.thereby effectively weakening it.Cavitation corrosion of cast aluminum alloy was weakened.It was further found that the cavitation corrosion of cast aluminum alloy in the new coolant was affected by the synergistic effect,and that the corrosion accelerated erosion process.The cavitation corrosion model of cast aluminum alloy in the new coolant was proposed.