Corrosion And Protection Of Pure Aluminum In Propylene Glycol Aqueous Solution

Propylene glycol aqueous solution can be used as antifreeze because of its low freezing point,degradability and environmental-friendly characteristics.Nowadays,the corrosion of propylene glycol aqueous solution on aluminum and its alloys has become a key problem restricting its application.Using corrosion inhibitors can solve this problem,but the corrosion and protection of pure aluminum and aluminum alloys in propylene glycol solution are still less studied.In this study,the electrochemical corrosion behavior of pure aluminum in propylene glycol solution was investigated by potentiodynamic polarization curve technology,EIS,SEM and static corrosion weight-loss experiment.The micro-morphology of pure aluminum after immersion in propylene glycol solution was observed.The inhibitor formula in propylene glycol solution was determined.The changes of different components of inhibitor formula on the inhibition efficiency were analyzed.The effects of chemical modification on corrosion inhibition efficiency were compared under different experimental conditions,and the adaptability of corrosion inhibitors to other metal was evaluated.Relevant data of pure aluminum,brass,copper,cast iron and 20#carbon steel were obtained.The results show that:(1)Propylene glycol aqueous solution is corrosive to pure aluminum.Varying propylene glycol concentration from 20%to 90%,the self-corrosive current density of pure aluminum decreases from 1×10-6 A/cm2 to 2×10-7 A/cm2,indicating that the corrosion of propylene glycol solution decreases with the increase of propylene glycol concentration;when the pH value changes from 4 to 9,the self-corrosive current density decreases first and then increases,and the minimum and maximum values are obtained at pH=6 and pH=9,the results show that the corrosion of propylene glycol is the strongest when the pH value is 9.The corrosion of propylene glycol solution increases gradually from 20? to 60?.(2)Inhibitor formula with high inhibition efficiency for pure aluminum is as follows:benzotriazole(5 g/L),urotropine(5 g/L),sebacic acid(5 g/L),sodium benzoate(8 g/L),sodium oleate(0.15 g/L)and sodium nitrate(5 g/L).The corrosion inhibition efficiency of the inhibitor is 97.2%.When the concentration of benzotriazole increases from 3 g/L to 7 g/L,the inhibition efficiency increases first and then decreases,the inhibition efficiency reaches the maximum when the concentration is 5g/L.As the concentration of urotropine and sebacic acid increases,the inhibition efficiency increases.(3)The inhibition efficiency of inhibitor formula is affected by temperature and pH value.When the temperature rises from 20? to 60?,the inhibition efficiency decreases from 95%to 85%;when the pH value changes from 4 to 9,the inhibition efficiency increases first and then decreases and reaches the maximum of 95%when the pH value is 7.The inhibition efficiency is the minimum when the pH value is 9.(4)Inhibitor formula also has excellent inhibition efficiency for brass,copper,20#steel and cast iron.According to the static weight-loss experiment,the inhibition efficiency of the inhibitor formula for the four metals is 91.1%,93.2%,96.8%and 85.2%,respectively.