What are the reasons for severe electrolytic passivation of copper?
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The company’s electrolysis process is experiencing severe passivation; it is initially suspected that this is caused by an excessively low level of chlorine in the electrolyte. Are there any other possible causes?
This post was last edited by mcc2006 on 2010-3-25 at 13:49. Regarding the reasons for passivation, there are currently two competing theories: the phase formation theory and the adsorption theory. The formed film theory suggests that the reason for metal anode passivation is the formation of a dense, well-covered solid layer on the anode surface, which acts as a DULI phase to separate the metal from the solution. According to adsorption theory, metal passivation does not require the formation of a new solid phase film; rather, it results from the adsorption of certain particles on the metal surface or on part of its surface, thereby creating an adsorption layer that alters the interface between the metal and the solution. This increases the activation energy for the anodic reactions, leading to a reduction in the reactivity of the metal surface. In the case of copper electrolysis, the formation of anodic passivation is mainly attributed to two factors: one is the residual impurity elements from the pyrometallurgical refining stage, such as nickel, oxygen, and lead. One is the influence of various parameters during the electrolytic refining stage, such as the electrolyte temperature and the electrolyte circulation rate. A method to address anode passivation is first to reduce the content of impurity elements such as Ni, O, and Pb in the anode plate, to lower the current density during electrolysis, and to add a certain amount of chloride ions, generally maintaining it at 40–80 mg/L.
The correct answer is upstairs! I have no choice but to admire it!
Under normal circumstances, the primary solution should be to maintain the chloride ions in the solution. At the same time, attention should be paid to the enrichment of other impurities.
We have been increasing the chlorine concentration in the electrolyte over the past two days, and it’s having some effect. Recently, I conducted tests and found that the lead and oxygen contents in the anode plate were not high, but the antimony content was relatively high, at 0.25%. It is preliminarily believed that the high antimony content consumes a large amount of chlorine, thereby causing passivation! ! Dear Tongren, are there any other methods to remove passivation? ?
The most direct factor in addressing anode plate passivation is controlling the temperature at which slag is formed during the refining stage; otherwise, the copper melt will form insoluble complexes such as nickel mica. The second point is to pay attention to controlling the temperature of the molten copper during casting, to avoid excessive oxygen absorption. And what LZ said is that the antimony content in the anode plates is as high as 0.25; it seems that the quality of your anode plates is below 99%. It is suspected that high levels of antimony can result in the formation of multiple arsenic-antimony residues during the arsenic removal process in the purification workshop, and this issue can also be resolved. But I think the root of the evil of anode plates lies not in electrolysis, but in refining.
We produce anode plates with high levels of antimony and nickel. If the high antimony content is to be reduced through refining, it results in higher fuel consumption and longer processing times; therefore, we are now looking for solutions from the electrolysis perspective.
6# nn7263297: What are the appropriate temperatures for refining and slag formation, as well as during copper extraction? Please give me some guidance!
There are many different phenomena associated with anodic passivation. I’m not sure what kind of situation you’re referring to>. A low chlorine content can be detected by observing the deposition at the cathode. The ratio of additives used is also important; however, it is recommended that you first clean the contacts of the conductive rods (through acid cleaning) or strengthen those contacts.
Is there an oxide on the surface of the anode plate? You can try soaking the anode plate in the electrolyte first before using it for electrolysis.
10# good0635: This isn’t an issue; our anode plates are soaked before use, with the appropriate acidity and duration to ensure that the oxide layer on their surface is removed.