7A52铝合金干湿交替情况下电偶腐蚀行为研究

Galvanic Corrosion in Cyclic Wet-Dry Immersion Test of 7A52 Aluminium Alloy

目的研究海洋环境下7A52铝合金在干湿周浸使用过程中的电偶腐蚀现象。方法实验配制3.5%的Na Cl水溶液浸泡试样,实验周期为504 h,全浸试样作为对比试样,在实验周期内一直浸泡在Na Cl水溶液中。测试试样干湿周浸情况下7A52与5A06,38Cr Si之间的电偶电流及电偶电压,使用SEM分析腐蚀后的表面形貌。结果 7A52-5A06干湿周浸试样电偶电流变化不大,全浸试样电偶电流较初期变化较大,后期电偶电流的大小只有初期电偶电流大小的1/8左右,7A52-38Cr Si全浸试样与干湿交替情况下电偶电流基本相同。随着试验的进行,干湿交替及全浸情况下电偶电流的差异逐渐变大,电偶电流增大约为实验初期的10倍;全浸情况下试样表面腐蚀产物较致密,干湿周浸情况下腐蚀产物较为疏松。结论在3.5%的Na Cl水溶液干湿周浸情况下,7A52-5A06,7A52-38Cr Si的平均电偶腐蚀速度要大于全浸状态下的平均电偶腐蚀速度,干湿周浸情况下,7A52-5A06,7A52-38Cr Si腐蚀后试样表面形态具有较大差异,5A06在相同实验条件下的耐腐蚀性要好于7A52。

Objective To investigate galvanic corrosion phenomenon of 7A52 aluminum alloy used in cyclic wet-dry immersion test in marine environment. Methods The sample was soaked in 3.5% NaCl solution in all of the test cycle of 504 hours, with full immersion as control. Galvanic current and galvanic voltage under cyclic dry-wet immersion condition between 7A52 and 5A06, 38CrSi were tested, and the surface morphology after corrosion was analyzed. Results The galvanic current of 7A52-5A06 cyclic wet-dry immersion sample changed little, and that of full immersion sample changed much in the early stage, and was only about 1/8 in the later stage. The galvanic currents of 7A52-38CrSi full immersion sample and cyclic wet-dry immersion sample were almost the same. With the progress of the experiment, the difference of galvanic current between cyclic wet-dry immersion sample and full immersion sample became bigger, with the galvanic current increasing about 10 times than that in the early stage. The surface corrosion products of full immersion sample were dense, while those were loose of cyclic wet-dry immersion sample. Conclusion Under the condition of cyclic wet-dry immersion in 3.5% NaCl solution, the average galvanic corrosion speed of 7A52-5A06 and 7A52-38CrSi was faster than under the condition of full immersion. Under the condition of cyclic wet-dry immersion, the surface morphology of 7A52-5A06 and 7A52-38CrSi had a big difference after corrosion, and the corrosion resistance of 5A06 was better than 7A52 under the same experimental conditions.