| High-strength steel is being used more and more,with the development of deep-sea exploration technology and the strengthening of marine development in China.In order to suppress the corrosion of steel in seawater environment,and avoid the danger of hydrogen embrittlement of high-strength steel due to excessive protection potential,it is extremely important to develop low voltage anode materials with better comprehensive performance.13 low voltage sacrificial anodes were designed by adding alloying elements Bi,Sn and Ce to the Al-Zn-Ga-Si anode,and tested by sacrificial anode electrochemical performance test,Polarization curve test,electrochemical impedance test,metallographic observation,micro-potential test and dissolution morphology observation.The comprehensive performance of various anode formulations was studied,and the effects of these alloying elements on anode performance were summarized.An Al-Zn-Ga-Si-Bi-Ce anode having a potential of-0.773 to-0.815 V,a current efficiency of 83%or more,and a good dissolution morphology is preferably used.By changing the test environment of the anode sample later,The changes of anode performance under temperature,dissolved oxygen concentration and deep sea alternating environment were studied.The results showed that:The Bi element has little effect on the grain size of the Al-Zn-Ga-Si system anode.After the addition of Bi,the actual capacity of the anode material is 2500A·h·kg-1or more,the current efficiency is about 85%,and the working potential meets the requirements.Bi can make the anode surface potential distribution more uniform and improve the dissolution morphology of the anode material.It is determined that the content of Bi in the low potential anode system is 0.05%.The Sn element can play a role in refining the crystal grains,and the actual capacitance and current efficiency of the anode material are significantly improved after the addition of Sn.However,it was found by polarization curve measurement that the anode region of the material has a certain passivation behavior.As the content of Sn in the anode material increases and the potential of the anode surface is gradually distributed,the solubility of the anode material is improved.It is determined that the content of Sn in the low potential anode system is 0.05%.The rare earth element Ce can play the role of refining the anode crystal grains in the anode.When the content is 0.1%,the anode grain refining effect is optimal.At this time,the anode operating potential ranges from-773 to-815 mV,which is in accordance with the low potential anode standard.The activity of the surface of the anode will increase first and then decrease as Ce increases.When the Ce content is0.1%,the oxide surface of the anode surface has the lowest resistance value,and the activation solubility and dissolution morphology are better.Therefore,the content of Ce in the anode is preferably 0.1%.The decrease in seawater temperature causes a positive shift in the open circuit potential,but the magnitude of the positive shift is small,approximately 50 mV.A decrease in the dissolved oxygen concentration causes a negative shift in the open circuit potential of the anode material,with an amplitude of about 100 mV.The low temperature causes the intergranular corrosion of the anode to increase and the anode dissolution morphology to deteriorate. |
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