Research On Effects Of Fe,Si Cu And In Contents On The Characterization Of Aluminum Alloy Sacrificial Anode

Aluminum alloy sacrificial anode materials have been widely used in anti-corrosion protections for all kinds of ships,oil platforms and other maritime infrastructure constructions.The methods of changing element contents or smelting process were adopted primarily in the present study of sacrificial anode at home and abroad.Nevertheless,there is very few research reports about the influence of impurity content on electrochemical properties of aluminum alloy anode.Therefore,it is very profound to investigate the effect laws of Fe,Si and Cu impurities on the electrochemical properties of aluminum alloy anode in seawater.The effects of Fe,Si and Cu impurity content on the electrochemical properties of Al-Zn-In-Mg-Ti sacrificial anode were investigated by the electrochemical method,scanning electrochemical microscopy measurements and observed by the modern physical analytic technology as SEM,EPMA and ICP-MS in seawater to obtain the following conclusions.The current efficiency of Al-5Zn-0.02In-1Mg-0.05Ti(wt.%)alloy reaches 92.89%in seawater by adding 0.10 wt.%Fe.The working potential of sacrificial anode is between-1.052?-1.067 V.And its actual capacitance is 2665.97 A·h·kg-1.The anode presents the enough negative open circuit potential,the good electrochemical polarization properties,the properties of low passivation film resistance and high electric double layer capacitance.While Fe content exceeds 0.1 wt.%,the resistance of active dissolution increases gradually.The anode current efficiency decreases obviously.The current efficiency of Al-5Zn-0.02In-1Mg-0.05Ti(wt.%)alloy reaches 85.42%in seawater by adding 0.09 wt.%Si.The working potential of sacrificial anode is between-0.918?-0.935 V.And its actual capacitance is 2450.94 A·h·kg-1.The number of isometric crystals increases and the average size of grain is 47?m,which indicates that the anode dissolve uniformly in the cathodic protection process due to the improved uniformity of alloy organization.While Si content exceeds 0.09 wt.%,it brings the increase of alloy's passivation film resistance and the reduction of current efficiency.The current efficiency of Al-5Zn-0.02In-1Mg-0.05Ti(wt.%)alloy reaches 93.22%in seawater by adding 0.005 wt.%Cu.The working potential of sacrificial anode is between-1.057?-1.078 V And its actual capacitance is 2674.73 A·h·kg-1.The alloy also has a good dissolution morphology.While the Cu content exceeds 0.005 wt.%,the resistance of alloy's passivation film increases gradually due to the increased viscosity of corrosion products.It indicates that the active dissolution and the current efficiency of anode decrease obviously.The current efficiency of Al-5Zn-0.02In(wt.%)alloy reaches 90.43%in seawater by adding 0.10 wt.%Fe,0.09 wt.%Si and 0.005 wt.%Cu.The working potential of sacrificial anode is between-1.086?-1,102 V.And its actual capacitance is 2595.34 A·h·kg-1.The surface of anode corrodes uniformly.It can provide the stable drive potential and corrosion current.It can produce the synergistic effect by adding Fe,Si and Cu together.Meanwhile,A universal effect law of content proportioning ratio for Al-Zn-In series of sacrificial anode has been proved.Al-5Zn-In-0.09Si-0.1Fe-0.005Cu(wt.%)alloy can polarize the protected metal and avoid the hydrogen evolution corrosion form the cathode space additionally by adding 0.02 wt.%In to obtain the moderate working potential in seawater.When the In content under 0.02 wt.%,the anode appears partial corrosion due to the inadequate activation.While In content exceeds 0.02 wt.%,a lot intercrystalline corrosion due to the superfluous precipitation phase is responsible for the falling of grains.It indicate that the current efficiency of aluminum alloy anode decrease obviously.