| Our country's oil and gas fields are widely distributed,and there are many types of storage tanks.The differences in environmental conditions have different requirements for the corrosion resistance of aluminum anode protection.The high salinity and high chloride ions in the storage tank are extremely corrosive to ordinary carbon steel.The research and development of aluminum alloy sacrificial anodes suitable for the medium environment of oil and gas field storage tanks is of great significance and imminent.As a sacrificial anode,aluminum alloy can better protect the steel substrate and extend the service life of steel-based equipment and auxiliary facilities.However,the current commonly used anodes have the problem of low protection efficiency,and it is necessary to increase their activity by adding alloying elements and performing appropriate heat treatment.Based on the difference in composition,the protective effect of aluminum alloy anodes on steel-based materials is also different.For this reason,based on the characterization of the sacrificial anode efficiency,this article hopes to improve the sacrificial anode protection efficiency through the method of element substitution.Based on this,this paper prepared Al-Zn-In anodes with different precipitation phases,and simulated the environment of a gas field sewage storage tank for experiments to study the effect of different precipitation on the protection performance of aluminum alloy sacrificial anodes.Characterized the metallographic structure and the types,sizes and distribution characteristics of precipitated phases.Combining Sn composition control to prepare high-efficiency anodes,and finally form a sacrificial anode with high protection efficiency,which provides a research foundation for the preparation of sacrificial anodes for sewage storage tanks.Studies have shown that after adding Cd to the Al-Zn-In anode,there are two types of precipitated phases:one is the small particle-like In-rich phase,and the other is the lamellar Zn Fe phase.The working potential of the Al-Zn-In-Cd anode in the sewage storage tank environment is-0.9671V,and the current efficiency is 46.19%.The dissolution process is dominated by the preferential dissolution mechanism of the second phase.The anode has a certain protective effect on the storage tank,but the protective effect on the position of the air/water interface is poor.After replacing Cd with Mg and Ti,there are two kinds of precipitated phases:one is the fine granular Mg Ti phase,and the other is the massive(Zn,Fe)-rich phase.The working potential of Al-Zn-In-Mg-Ti is-1.0781V,and the current efficiency is 65.41%.The second phase preferential dissolution mechanism is the main.The anode avoids local corrosion of the storage tank to a certain extent,and can better protect the base of the storage tank,but there is still a problem of low efficiency.After replacing Ti with Sn,there are two types of precipitated phases:one is spherical In3Sn phase,and the other is elongated Sn Fe phase.The working potential of Al-Zn-In-Mg-Sn is-1.1255V,and the current efficiency is 73.55%.The main mechanism is"dissolution-redeposition".The protective effect of the anode on the base of the storage tank is significantly improved,and it is more suitable as a sacrificial anode protection material for the sewage storage tank.With the continuous increase of Sn element,the grain size of Al-Zn-In-Mg-x Sn metallographic structure gradually decreases,and the grain boundary gradually narrows.However,the size of the second phase gradually increased,and the number also increased.When Sn is 0.15%,the dissolution is more uniform,and"dissolution-redeposition"is the main form.The spherical rich(Sn,In,Mg)second phase plays a significant role in the electrochemical corrosion process,the self-corrosion potential has the smallest positive shift trend,the self-corrosion current density is the smallest,and the impedance arc size is moderate,which is beneficial to Al-Zn-In-Mg-0.15Sn forms a more uniform corrosion morphology. |
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