ABSTRACT: Copper and copper alloys have good corrosion resistance, especially in complex and harsh marine environment with good corrosion resistance. With the development of marine industry, it is very important for the application of copper and copper alloy in marine industry to excavate the deep corrosion resistance of copper and copper alloy, prolong its service life and reduce its cost. In this paper, the corrosion spalling behavior of copper and copper alloys is studied, the corrosion spalling behavior of five copper and copper alloys in different marine environments is compared, and the weight loss and surface state of five copper and copper alloys are recorded and analyzed, it provides the basic theoretical basis for improving the corrosion resistance of copper and copper alloys.

Key words: copper; Copper Alloy; corrosion resistance. Classification number: TG146.11 literature identification number: A

Copper and copper alloys have good corrosion resistance, especially in the complex and harsh marine environment. Therefore, copper and copper alloys are widely used in marine industrial materials. The chemical composition of copper alloy is closely related to its corrosion resistance. According to relevant research, nickel is added to copper, and the electrochemical test of the alloy shows that the current passing through the alloy is obviously lower than that passing through pure copper, the results show that Cu-ni alloy can effectively improve its corrosion resistance. In addition, high zinc copper, tin bronze, aluminum bronze and aluminum bronze are composed of mixed zinc element, tin element and aluminum bronze in pure copper. Copper and copper alloys in the marine environment can produce copper ion, with the role of detoxification, can remove marine organisms, with good pollution resistance. According to the different performance requirements of materials, different elements can be added to form copper alloy in order to achieve its performance. According to the research, the tin bronze with a certain amount of tin has good corrosion resistance and can form a dense tin compound film to prevent the further corrosion of copper alloy when electrochemical reaction takes place in the marine environment, in addition tin bronze also has good strength and hardness. Aluminum brass

The reason why aluminum in aluminum brass can react with oxygen to form dense alumina film is that it can prevent further corrosion of aluminum brass. The results show that copper alloys with iron and manganese not only have excellent corrosion resistance, but also have good stain resistance. Therefore, it will play an important role in the research of corrosion and spalling of copper and copper alloy. Sentence is too long, please supply a shorter sentence. In addition, there are erosion corrosion, fatigue corrosion and so on. In different marine environments, different corrosion processes are also dominant. In this paper, the corrosion spalling behavior of copper and copper alloys is studied, the corrosion spalling behavior of five copper and copper alloys in different marine environments is compared, and the weight loss and surface state of copper and copper alloys are recorded and analyzed.

1. The corrosion resistance of copper and copper alloys was tested for the corrosion and exfoliation behavior of copper and copper alloys. Five copper and copper alloys were selected for corrosion resistance test.

The selected copper and copper alloys should be cut into regular sheets of 30 cm in length, 20 cm in width and 2 ~ 5 mm in thickness, with 3 parallel specimens, deoiling, deionized water washing, Alkali washing, deionized water washing, acid washing, deionized water washing and anhydrous alcohol washing are carried out respectively. In order to verify the corrosion and spalling behavior of copper and copper alloy in seawater, Qingdao was selected as the full exposure test site. The copper and copper alloy were placed at different water levels, and the test surface should be vertical to the water surface, the deposition height of copper and copper alloy is divided into splash zone, tidal zone and immersion zone according to different marine environment. The depth of corrosion is shown in Table 2.

Copper and copper alloys were immersed in different marine environments for 4 cycles (10 days each cycle) . The sample state and weight loss were observed and recorded in each cycle. 2. The results show that copper and copper alloys are tested in splash zone, tidal zone and immersion zone respectively. After 4 cycles of observation and recording, the calculated average values are shown in table 3.

According to the results of weight loss of copper and copper alloys in different marine environments, the percentages of weight loss of Red Copper in splash zone, tidal range zone and immersion zone are higher than the average percentages of each zone, it is also proved that the corrosion resistance of copper alloys is better than that of copper alloys, and the average weight loss percentage of tin bronze in the full immersion zone and the tidal zone is not much different, and the average weight loss percentage is much higher than that of other copper alloys, in the immersion zone, the average weight loss percentage of copper alloy has no significant difference, which proves that the corrosion resistance of Tin Alloy in tidal range is lower than that of other copper alloys. Compared with the average weight loss percentage in splash zone, tidal zone and immersion zone, the corrosion resistance of copper and copper alloys is from high to low in splash zone: Tin Bronze, aluminum bronze, copper-nickel alloy, aluminum brass, red copper; The corrosion resistance in tidal zone is from high to low: Cu-ni Alloy, al-bronze, al-brass, sn-bronze and Cu-cu. The corrosion resistance of copper and copper alloys is the lightest in the splash zone. Although the splash zone is the closest to the atmosphere and rich in oxygen, which provides a good environment for corrosion, the corrosion of copper and copper alloys is the lightest in the splash zone, this may be due to the passivation of copper and copper alloys in contact with air to form a dense oxide film, which can effectively reduce corrosion. The corrosion resistance of copper and copper alloys is the most serious in the whole immersion zone. In addition to the corrosion in the whole immersion zone, the corrosion in the whole immersion zone also comes from the velocity of the seawater, the temperature of the seawater, the adhesion of microorganisms, the erosion of sediment, etc. , the processing technology of copper and copper alloy itself will also have a very important influence, in this area the performance of copper-nickel Alloy and aluminum-brass is obviously weaker than that of other copper alloys, it is likely that cu-ni alloys and al-brass are less resistant to marine organisms than other alloys. The corrosion resistance of copper and copper alloys is that the tidal zone is between the splash zone and the immersion zone. The corrosion in this zone is mainly uniform corrosion, accompanied by local corrosion, the corrosion resistance of Tin Brass in this area is obviously weaker than that of other copper alloys, and the corrosion resistance of other copper alloys in this area is obviously better than that in the whole immersion area. The macrographs of copper and copper alloys show pit-like corrosion, local skin-like porosity in copper alloys and pit-like corrosion in copper alloys. The corrosion of red copper is more serious than that of other copper alloys. It can be concluded that the corrosion resistance of copper alloy is better than that of copper in marine environment. According to the surface corrosion condition, the corrosion degree of the whole immersion zone is from low to high: Tin Bronze, aluminum bronze, aluminum brass, copper-nickel alloy, red copper. Fig. 1 is the macrograph of copper and copper alloy after immersion zone test (1,2,3,4,5 represent copper, copper-nickel alloy, aluminum brass, aluminum bronze and tin bronze respectively) .

There are many kinds of ocean corrosion, such as electrochemical corrosion, chloride ion corrosion, impact corrosion, ocean microorganism corrosion and so on. In addition to local corrosion, there are pitting corrosion, crevice corrosion, stress corrosion and fatigue corrosion. The key to prevent corrosion and prevent further corrosion is the selection of materials, copper and copper alloys are able to meet the requirements of marine materials. However, copper and copper alloys can also produce corrosion, these factors are diverse. The first is the adhesion of marine organisms to the surface of copper and copper alloys. The sulfides produced by marine organisms can further promote the corrosion of copper and copper alloys, in the process of sand erosion, the oxide film on the surface of copper and copper alloy will fall off, which will cause the corrosion of copper and copper alloy, the surface stress state of copper and copper alloy is different because of different processing technology, and the surface structure is different, which affects the corrosion resistance of copper and copper alloy. The sediment in seawater also has a great influence on the corrosion and spalling of copper and copper alloys. The erosion of sediment can accelerate the corrosion rate of copper and copper alloys and form pitting corrosion and local corrosion. The Ph of seawater also affects the corrosion of copper and copper alloys. In general, copper and copper alloys are more prone to corrosion in acidic environment and more difficult to corrosion in alkaline environment, this may be due to the fact that the metals in copper and copper alloys react more easily in acidic conditions, especially the dense oxide film on the surface of copper and copper alloys. In addition, the ions in seawater also affect the corrosion resistance of copper and copper alloys, such as sulfate, chloride ion, etc. . For the complex marine environment, there are many reasons that affect the corrosion and spalling behavior of copper and copper alloys. 3. Conclusion by studying the corrosion and spalling behavior of copper and copper alloy, the conclusions are as follows: 1) the corrosion resistance of copper alloy is better than that of copper; 2) the corrosion resistance of tin bronze is worse than that of other copper alloys in tidal range; 3) the corrosion resistance of copper and copper alloys in marine environment is better in splash zone than in tidal range, and better in tidal range than in immersion zone. Although it is proved that the corrosion resistance of Copper Alloy in splash zone, full immersion zone and tidal zone is obviously higher than that of copper alloy, copper can produce more copper ions in the marine environment, and can effectively reduce the corrosion caused by marine organisms. However, the corrosion resistance of copper alloy in full immersion zone and tidal zone is still lower than that of copper alloy.

 Source: Chinanews.com, by Guan Mengen

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