Electrochemical Properties Of High Active Aluminum Alloy Sacrificial Anode In Deep Sea

The development and utilization of oil and natural gas have been depleting such land resources.According to the statistics,oil and natural gas of the South China Sea occupy one third of China's total oil and gas resources,but 70%of the resources are contained under the sea which is about 300 meter below the deepwater area.The development and utilization of these resources lead to the deployment of deep-sea oil projects.When the traditional sacrificial anodes are used to protect the marine metal facilities in the shallow sea,its electrochemical performance is excellent,but the problem of surface dissolution,potential positive displacement and low current efficiency can be occurred in the deep sea,which seriously affects the protection ability of sacrifice anode on metal components.Therefore,in order to develop the electrochemical performance of aluminum sacrificial anode in deep sea,this paper used the current marine anti-corrosion alloy of Al-Zn-In-Si and Al-Zn-In-Mg-Ti as the research object,using heat treatment effect as the studying target,and determined its electrochemical performance with the affect of alloy composition and deep-sea environment.By studying the influence of the cooling rate,casting method,heat treatment time and heat treatment temperature on the electrochemical performance of Al alloy sacrificial anode,the corresponding results could be obtained:Electrochemical properties is relevant not only to elements in the composition of the alloy and alloy solid solubility,but also to the second phase and the segregation phase of the alloy.The second phase and phase segregation is too small which would cause the alloy pitting process hard to be carried out,the oxide film on the surface of alloy hard to destroy,Alloy potential shift,However,too much of the second phase and segregation of the alloys will lead to the alloy pitting corrosion,the corrosion rate increased and the current efficiency decreased.Research shows that the second phase and segregation phase is reasonable through the water cooling after the heat preservation of 4h at 500?.In this case,the anodic current efficiency is increased,the corrosion potential is negative,and the corrosion products are easy to fall off,the dissolution morphology is uniform,the comprehensive performance is the best.The effect of different Fe contents to the Electrochemical properties of Al-Zn-In-Si and Al-Zn-In-Mg-Ti anodic alloys was studied:The increase of Fe content can seriously affect the activation dissolution of Al-Zn-In-Si alloy,the higher the content of Fe,the corrosion of the alloy is more serious,the current efficiency of the alloy is lower.Especially when the content of Fe is over 0.2%,the current efficiency of the alloy is reduced to 50%.However,the increase of Fe content has little effect on the activation dissolution of Al-Zn-In-Mg-Ti anodic alloy,and will also make the corrosion potential of the anodic alloy negative shift.The Electrochemical properties of the Al-Zn-In-Mg-Ti anode alloy are better first and then worse with the increase of Fe content,and the electrochemical performance of the anodic alloy is the best when the content of Fe is about 0.15%.The effect of seawater temperature,oxygen content and salinity to the Electrochemical properties of Al alloy sacrificial anodes is studied:The decrease of the temperature can decrease the activity of the active element in the alloy,slow the pitting corrosion of the initial alloy and makes the alloy dissolve more uniform.The decrease of oxygen content is beneficial to the sTableility of the alloy working potential.But the decrease of the temperature and the decrease of the oxygen content are beneficial to the adhesion of the dissolution products of the anode,when the content of Fe in the alloy exceeds the standard,the coral dissolution morphology will make the dissolved products more easily attached,which will causethe alloy surface coated with a dense dissolution product and the alloy eparated from the seawater.Salinity had no significant effect on the sacrificial anode in seawater.Therefore,in order to obtain the high active aluminum base sacrificial anode,the cooling rate should be controlled during the alloy casting,so that the second phase and the segregation phase can be distributed uniformly and size.The Al-Zn-In-Si anode alloy whose Fe content is less than 0.1%should be used in preference,but considering the economic benefits,the Al-Zn-In-Mg-Ti sacrificial anode can be used whose Fe content is between 0.1%?0.15%.