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Analysis of a centreline failure of a lead alloy anode used in the copper electro-winning process
Engineering Failure Analysis ( IF 4.4 ) Pub Date : 2020-11-27 , DOI: 10.1016/j.engfailanal.2020.105057
A. Elrefaey , Y. Gu , J.D. James , C. Kneen , I. Crabbe , J. Sienz

Thousands of lead anodes are currently used in the electro-winning of copper across the globe. The corrosion and the electrochemical performance of these anodes significantly affect the economy of the process. Premature failure of anodes is often a problem for the commercial operators of tank houses. Recently, the authors were asked to advise on an unusual case where a lead alloy anode split at almost the centreline of the cross section. Different characterization techniques were employed to detect the cause of failure. The fractured samples were metallographically examined with an optical microscope and a Scanning Electron Microscope (SEM) equipped with Energy-Dispersive X-ray Spectroscopy (EDS) analysis. Different phase at the fracture surface were also identified by X-Ray Diffraction technique.

The failure mechanism of this anode appears to be manganese contaminated electrolyte attacking the anode perimeter, leading to initial corrosion sites and compounded by subsequent exfoliation corrosion through inter-granular attack and further formation of manganese dioxide. The established practice of producing lead alloy anodes via rolling confers beneficial properties to the finished anodes. However, the resulting elongated grains can in some cases, where the electrolyte is contaminated with elements that are prejudicial to stable oxide layer formation, cause susceptibility to exfoliation corrosion.



中文翻译:

铜电铸过程中铅合金阳极中心线失效的分析

目前,全球有成千上万的铅阳极用于电解铜。这些阳极的腐蚀和电化学性能极大地影响了工艺的经济性。阳极的过早失效对于罐房的商业运营商来说通常是一个问题。最近,作者被要求就一种不寻常的情况提供建议,其中铅合金阳极几乎在横截面的中心线处裂开。采用了不同的表征技术来检测故障原因。用光学显微镜和配备有能量色散X射线光谱法(EDS)分析的扫描电子显微镜(SEM)对断裂的样品进行金相检查。还通过X射线衍射技术确定了断裂表面的不同相。

该阳极的失效机理似乎是锰污染的电解液侵蚀阳极周边,导致最初的腐蚀部位,并随后由于晶间腐蚀而剥落腐蚀并进一步形成二氧化锰,从而加剧了腐蚀。通过轧制生产铅合金阳极的既定实践赋予成品阳极有利的性能。然而,在某些情况下,当电解质被有害于稳定氧化物层形成的元素所污染时,所得的细长晶粒会引起剥离腐蚀的敏感性。

更新日期:2020-12-01
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