Efficient Al alloy sacrificial anode suitable for low-temperature seawater environment and preparation process thereof

Abstract

The invention discloses an efficient Al alloy sacrificial anode suitable for a low-temperature seawater environment, and belongs to the field of corrosion and protection. The efficient Al alloy sacrificial anode is characterized in that Al is taken as a raw material, and Zn, In, Sn and Bi alloy elements are added so as to eliminate the influence of impurity elements to the electrochemical performance of the sacrificial anode; the efficient Al alloy sacrificial anode comprises the following components by weight percent: 3.2% to 5.8% of Zn, 0.005% to 0.01% of In, 0.016% to 0.02% of Sn, 0.01% to 0.2% of Bi, less than or equal to 0.10% of impurity element Fe, less than or equal to 0.1% of impurity element Si, less than or equal to 0.005% of impurity element Cu and the balance of Al. The efficient Al alloy sacrificial anode has the electrochemical performance that the working potential of the sacrificial anode is stabilized within -1.05V to -1.1V (relative to SCE (Saturated Calomel Electrode)), corrosion products easily fall off, the corrosion morphology is evenly dissolved, the capacitance of the sacrificial anode is greater than or equal to 2700A.h / kg and the current efficiency of the sacrificial anode is greater than or equal to 95% under the conditions that the seawater temperature is within 0 DEG C to 5 DEG C. Thus, the efficient aluminum alloy sacrificial anode can be used for the cathode protection of a metal-structured article under the low-temperature seawater environment.

Description

[0001] technical field [0002] The invention belongs to the field of corrosion and protection, and relates to a high-efficiency aluminum alloy sacrificial anode for cathodic protection of metal structures and equipment in a low-temperature seawater environment. [0003] Background technique [0004] The low-temperature environment in the ocean mainly includes two areas: one is the surface seawater at high latitudes, where the seawater temperature is lower than 5°C in winter, and even freezes; the other is the deep sea area, where the seawater temperature changes with the increase of seawater depth, For example: the surface temperature of seawater in the Gulf of Mexico is room temperature, and when the seawater depth increases to 610 meters, the seawater temperature drops to 5°C. In the Norwegian Sea, the Atlantic Ocean and the Pacific Ocean, and even tropical seas such as Brazil and the Western Pacific Ocean, the seawater temperature in the deep sea is almost the same low ...

AI Technical Summary

Problems solved by technology

[0005] Due to the rich oil and gas resources and ore resources in the ocean, countries all over the world are increasing the development and utilization of the ocean. The development of the ocean will inevitably involve the development and protection of ocean engineering equipment, and the ocean environment is the most harsh corrosion environment. In this environment, metal structures and equipment will suffer severe corrosion damage, resulting in a greatly reduced service life

At present, most offshore offshore platforms and submarine pipelines use sacrificial anodes for cathodic protection, but at present, sacrificial anodes in the domestic marine environment mainly use Al-Zn-In, Al-Zn-In-Cd and Al-Zn-In-Mg-Ti , this kind of anode has stable electrochemical performance in the normal temperature environment of the offshore sea area, the capacitance is 2450-2600A h / Kg, the dissolution is uniform, and the corrosion products are easy to fall off

However, in low-temperature seawater environment, the current efficiency of Al-Zn-In sacrificial anode is 87%, the working potential is shifted to -1.0V, and the dissolution is uneven, so it is not suitable for use under low temperature conditions; Al-Zn-In-Cd sacrificial anode The current efficiency at low temperature is 84%, the working potential is shifted to -1.0V, the corrosion product does not fall off, and the dissolution is uneven, so it is not suitable for use at low temperature; Al-Zn-In-Mg-Ti sacrificial anode is at low temperature The lower current efficiency is 90%, and the working potential is negative to -1.05V. However, after a 7-month field test of the anode, a large amount of corrosion products adhered to the surface of the anode, resulting in severe intergranular corrosion and grain shedding. occurs, cannot be used normally

Another patent 200810249621.8 discloses an aluminum alloy sacrificial anode suitable for deep sea environment, its composition is Al-Zn-In-Mg-Ti-Ga-Mn, the working potential of the anode in low temperature environment is -1.05~ -1.10V, the current efficiency is 90%, but this sacrificial anode has many added elements, the melting process is complicated, and the cost is high, which is not conducive to industrial production

[0006] In short, there are two shortcomings in the existing sacrificial anodes: one is that the electrochemical performance is not high, the potential is too positive, and the current efficiency is low; the other is that the melting process is complicated and the cost is high

The present invention overcomes the above deficiencies, and develops a high-efficiency Al-Zn-In-Sn-Bi five-element aluminum alloy sacrificial anode suitable for low-temperature seawater environments. At present, the anode has not been reported in the literature

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