Study on the behavior of Zn–Fe alloy electroplating

Zhang, Z.; Leng, Wenhua; Shao, Haibo; Zhang, J.Q.; Wang, J.M.; Chen, Cao

doi:10.1016/s0022-0728(01)00665-9

Cited by 63 publications

(24 citation statements)

References 8 publications

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“…3 for the same experimental conditions as those explained above. It is noteworthy that iron does not deposit with zinc in a normal way but following the anomalous codeposition process [15,16,22]. Therefore, in the case of the OCR experiments, iron deposition begins when zinc concentration diminishes, approximately, to 50%.…”

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“…The AEM acted as a barrier for the chlorine gas that could not reach the cathodic compartment preventing the zinc redissolution phenomenon. However, in the absence of chlorine, iron began to codeposit with zinc following an anomalous codeposition phenomenon [14][15][16] as although iron is more noble than zinc, it deposits preferentially.In order to prevent iron codeposition, in this paper the AEM is changed to a cationic exchange membrane (CEM), NAFION-117. The spent pickling baths are placed in the anodic compartment since the NAFION-117 membrane permits the zinc pass to the cathodic compartment preferentially over iron.…”

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Treatment of spent pickling baths coming from hot dip galvanizing by means of an electrochemical membrane reactor

2014

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The performance of a one (OCR) and a two-compartment electrochemical reactor in the presence of a cation-exchange membrane (CEM) for the zinc recovery present in the spent pickling baths is analyzed in this paper under galvanostatic control. These solutions, which mainly contain ZnCl 2 and FeCl 2 in aqueous HCl media, come from the hot dip galvanizing industry. The effect of the applied current, the dilution factor of the baths and the presence or absence of initial cathodic zinc is also studied.For the 1:50 diluted spent bath, OCR experiments initially present higher values of the figures of merit than those obtained in the presence of the CEM since zinc is close to the cathode from the first electrolysis instants. However, at long electrolysis times, OCR presents zinc redissolution for all the current values tested due to the chlorine and iron presence close to the zinc deposits. In addition, the iron codeposition phenomenon is also observed in the OCR experiments when pH values are close to 2. On the other hand, CEM experiments become very similar to the OCR experiments at long time values since the CEM under these experimental conditions prevents zinc redissolution phenomenon and also iron codeposition. 2When the 1:50 diluted bath is concentred to 1:10, OCR experiments present the same tendency as that observed for the 1:50 dilution factor but the effect of zinc redissolution is increased due to the greater amount of chlorine generated in the anode. Under these experimental conditions, iron deposition has also been observed in the presence of the cation-exchange membrane as the rate of zinc deposition is greater than that of zinc transport through the membrane, and the zinc/iron ratio in the cathodic compartment is not high enough to prevent iron codeposition. In both cases, the pH values when iron codeposits with zinc is close to 2 and the zinc/iron ratio is below 0.6. The presence of initial zinc in the cathodic compartment of the electrochemical reactor enhances the reactor performance since allows the zinc-iron separation in one single step and avoids the zinc redissolution phenomenon. 1-IntroductionThe pickling step, previous to the galvanized process, consists of attacking the surface of the pieces with HCl in order to clean them from rust and impurities. This process generates a succession of effluents containing, among other substances, high concentrations of ZnCl 2 , FeCl 2 and HCl [1]. The composition of these baths depends on the kind of the pieces cleaned. If the pieces pickled are new ones, an iron rich effluent will be obtained, whose typical composition is 100-160 g/l of Fe, 5-10 g/l of Zn and 30-50 g/l of HCl; but if these pieces have previously been galvanized, the effluent would be rich in zinc and its typical composition would be 10-20 g/l of Fe, 80-230 g/l of Zn and 10-30 g/l of HCl. Finally, if both kinds of pieces are treated, a mixture effluent will be obtained, whose typical composition is 80-120 g/l of Fe, 20-60 g/l of Zn and 30-50 g/l of HCl [2]. The production of the spent ...

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Treatment of spent pickling baths coming from hot dip galvanizing by means of an electrochemical membrane reactor

2014

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“…3. It is noteworthy that iron does not deposit with zinc in a normal way but following the anomalous codeposition process [14][15][16]. This fact explains that iron deposits from the beginning of the electrolysis for the CEM experiments.…”

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Study of the zinc recovery from spent pickling baths by means of an electrochemical membrane reactor using a cation-exchange membrane under galvanostatic control

Carrillo-Abad

García-Gabaldón

Pérez-Herranz

2014

Separation and Purification Technology

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to reach the equilibrium between the zinc transferred through the membrane and that deposited on the cathode. Therefore, the synthetic cathodic zinc is not consumed at any time. Moreover, under this circumstances iron codeposition is also avoided. INTRODUCCTIONOne of the most well known uses of metallic zinc is to protect iron or steel pieces from corrosion processes by coating them with it [1]. In order to coat the pieces, the oldest technique used is the hot dip galvanizing, which is based on dipping the pieces into molten zinc. Previously to the dipping process, these pieces must be cleaned by means of different pretreatments. The present paper focuses on the effluents coming from the pickling process, which consists of attacking the pieces surface with HCl for cleaning them from rust and impurities. The effluents coming from the pickling process contain high concentrations of Zn, Fe and HCl together with low concentrations of organic compounds, such as hydrogen evolution reaction inhibitors, and other heavy metals [2].Therefore, spent pickling baths have to be treated before their disposal to accomplish with the environmental restrictions. However, the development of an adequate treatment for this effluent is very difficult because of the high complexity usually encountered in the hydrochloric acid effluents, where the target species are present in a heterogeneous mixture with different amounts of non-desirable compounds [3].Owning to the inefficiency of the traditional methods for the treatment of spent pickling baths, as the precipitation-filtration process [4], many different techniques such as liquid-liquid extraction [5] or anionic resins [6] have been suggested [7]. In this way, the electrolysis in a membrane reactor is presented in this paper as an alternative for the treatment of the spent pickling baths in one single step. In a previous work [8], the authors performed an electrochemical study of the solution to obtain the kinetics of the electrochemical processes and, then, an undivided electrochemical batch reactor was used in potentiostatic and galvanostatic mode [9,10] to determine the viability of zinc recovery from spent pickling baths. During these experiments zinc redissolution was observed at high time values for all the experimental conditions. This process is related to the synergic effect of iron ions and dissolved chlorine gas that attacks zinc deposits causing their oxidation [11,12]. 3In order to prevent the zinc redissolution phenomena, an anion-exchange membrane (AEM) was initially used [13] to avoid chlorine presence in the cathodic compartment.This membrane permitted zinc conversion values closer to 100% and higher current efficiencies. However, iron began to codeposit with zinc as the latter was being removed from the solution since the iron-zinc system deposits following the anomalous codeposition phenomenon [14][15][16], in which the less noble metal (zinc) deposits preferentially, and iron deposition depends on the zinc-iron ratio, the applied current and the pH value.Therefore...

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“…The evolution of E observed in Fig. 9 is consistent with the anomalous co-deposition theory.The electrodeposition of zinc alloys with the eight group metals (Ni, Co and Fe) is classified as anomalous co-deposition, according to the Brenner definition [18][19][20], because the less noble metal deposits preferentially on the cathode with respect to the nobler one. In our case, when zinc is electroplated from an acidic electrolyte containing an iron group element, the less noble zinc is most often deposited preferentially.…”

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Recovery of zinc from spent pickling solutions using an electrochemical reactor in presence and absence of an anion-exchange membrane: Galvanostatic operation

Carrillo-Abad

García-Gabaldón

Ortega

et al. 2012

Separation and Purification Technology

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ElsevierCarrillo Abad, J.; García Gabaldón, M.; Ortega Navarro, EM.; Pérez-Herranz, V. (2012). Recovery of zinc from spent pickling solutions using an electrochemical reactor in presence and absence of an anion-exchange membrane: Galvanostatic operation. Separation and Purification Technology. 98:366-374. doi:10.1016/j.seppur.2012.08.006. Keywords: electrochemical deposition, chlorine, iron, redissolution, pickling solutions, zinc electrodeposition 1 RECOVERY OF ZINC FROM SPENT PICKLING SOLUTIONS USING AN ELECTROCHEMICAL REACTOR IN PRESENCE AND ABSENCE OF AN ANION-EXCHANGE AbstractThe performance of a one and two-compartment electrochemical reactor under galvanostatic control for zinc recovery present in the spent pickling solutions is studied in this paper. These solutions, which mainly contain ZnCl 2 and FeCl 2 in aqueous HCl media, come from the hot dip galvanizing industry. The effect of the anion-exchange membrane (AEM) on the figures of merit of the electrochemical reactor is analyzed.In the absence of iron in solution, as the current value was shifted towards more negative values, the zinc fractional conversion increased because of the increase in the 2 zinc reduction rate. However, the increase in current values made current efficiency decrease due to the hydrogen-reduction side reaction, which caused an increment in the specific energy consumption. The presence of iron in synthetic solutions led to a decrease in current efficiency associated with the reverse redox Fe 2+ /Fe 3+ system and to the enhancement of the HER, which also induced increments in the local pH and the subsequent zinc redissolution. These adverse effects related to the presence of iron could be minimized by the interposition of an AEM. In this case, the zinc redissolution was eliminated which enabled zinc conversion values close to 100% together with higher current efficiencies as the consumption of current by the system Fe 2+ /Fe 3+ was diminished.3 1-IntroductionHot dip galvanizing processes offer a simple and effective way for corrosion protection of steel parts. This protection is based on covering the steel with a thin layer of metallic zinc that protects steel from corrosion by two ways: surface coating and sacrificial anode as zinc is lees noble than iron. This process consists of the following steps: HCl. This gives rise to an environmental problem that has to be solved due to the hazardous nature of the effluents [2,3]. In addition, the decrease of natural reserves of non-ferrous metals and the requirement of environmental protection make zinc electrowinning from spent pickling solutions an interesting alternative [4,5]. Moreover, the electrolytic recovery of zinc present in the spent pickling baths is a suitable technique because zinc electrowinning has been practiced for many years [6]. In fact, 80% of world zinc production is obtained by electrowinning [1].In our previous paper [7], the potentiostatic recovery of zinc present in the spent pickling bath using an electrochemical reactor was studied. The major interfering re...

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Study on the behavior of Zn–Fe alloy electroplating

Cited by 63 publications

References 8 publications

Treatment of spent pickling baths coming from hot dip galvanizing by means of an electrochemical membrane reactor

Treatment of spent pickling baths coming from hot dip galvanizing by means of an electrochemical membrane reactor

Study of the zinc recovery from spent pickling baths by means of an electrochemical membrane reactor using a cation-exchange membrane under galvanostatic control

Recovery of zinc from spent pickling solutions using an electrochemical reactor in presence and absence of an anion-exchange membrane: Galvanostatic operation

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