The Anomalous Codeposition of Iron-Nickel Alloys

Dahms, Harald; Croll, I. M.

doi:10.1149/1.2423692

Cited by 380 publications

(220 citation statements)

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“…Therefore, in the case of the OCR experiments, iron deposition begins when zinc concentration diminishes, approximately, to 50%. This agrees with the model suggested by Dahms et al [23] who proposes that zinc inhibits iron deposition by the formation of a hydroxide film on the cathode surface. Therefore when zinc-iron ratio is low, the amount of zinc ions near the cathode diminishes, then, the film becomes weaker and iron begins to deposit.…”

Section: 1-1:50 Diluted Spent Pickling Bathsupporting

confidence: 92%

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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Section: 1-1:50 Diluted Spent Pickling Bathsupporting

confidence: 92%

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

2014

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“…[4][5][6][7][8][9][10][11][12][13] Since the magnetic properties of FeNi alloy change greatly depending on its composition, the alloy of fixed composition should be deposited stably to keep the desired properties. Therefore, it is important to make clear the mechanism of anomalous deposition of Fe-Ni alloys.…”

Section: Introductionmentioning

confidence: 99%

Mechanism of Anomalous Type Electrodeposition of Fe-Ni Alloys from Sulfate Solutions

et al. 2004

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The electrodeposition of Fe-Ni alloys was performed galvanostatically in the sulfate solutions of pH 1-3 at 40 C and the alloy deposition behavior was compared with that of Zn-iron-group metal alloys to investigate their codeposition mechanism. The deposition behavior of Fe-Ni alloy showed a typical feature of the anomalous codeposition, in which electrochemically less noble Fe deposits preferentially under most plating conditions. The anomalous codeposition behavior in Fe-Ni alloy deposition was evidently dependent on the pH buffer capacity of the solutions. This can be explained in terms of the preferential adsorption of FeOH on the deposition sites of more noble Ni due to the extremely smaller dissociation constant of FeOH þ than NiOH þ in the multi-step reduction process of hydrated iron-group metal ions.

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“…Observa-se que, na região I, predomina a redução de hidrogênio e na região II a (7) , que indicam que o comportamento anômalo é observado na eletrodeposição de ligas que contêm metais susceptíveis a hidrólise (Ni, Fe, Co, Zn).…”

Section: Discussionunclassified

“…Entre as hipóteses encontradas na literatura a mais difundida, e também alvo das principais controvérsias, é a proposta de Dahms e Croll. (7) Nela os autores sugerem que a adsorção do hidróxido do metal menos nobre (Fe(OH) 2 ), resultante do aumento do pH devido à evolução de hidrogênio, inibiria a redução do metal mais nobre (Ni), enquanto promoveria uma maior redução de ferro. No entanto, outros estudos sugerem que a codeposição anômala poderia ocorrer sem o aumento do pH.…”

Section: Introductionunclassified

CARACTERIZAÇÃO ELETROQUÍMICA E MORFOLÓGICA DE LIGAS Ni-Fe OBTIDAS EM SOLUÇÕES DE SULFATO

Santana

Díaz

Barcia

et al. 2012

TMM

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ResumoO comportamento de ligas NiFe é objeto de intensa investigação devido ao grande número de aplicações desses materiais no meio industrial. A eletrodeposição é um dos processos mais utilizados para produção dessas ligas devido ao seu baixo custo e sua capacidade de recobrir geometrias complexas. Variáveis do processo, como pH, densidade de corrente e composição do banho, podem afetar a cinética de deposição da liga bem como a morfologia e a estrutura dos depósitos obtidos. O objetivo do presente trabalho é estudar o efeito do pH sobre a cinética de deposição, composição e morfologia dos filmes. Os resultados das curvas de polarização e análise química mostram duas regiões: a primeira refletindo a redução de H + . Com aumento da polarização a corrente passa a variar fortemente com o potencial e a redução metálica ocorre com boa eficiência. A morfologia dos filmes varia com o pH da solução. Em pH 5, os depósitos são homogêneos e compactos. Para menores valores de pH (pH 1), são observadas trincas ao longo da superfície. Palavras-chave: Ligas níquel-ferro; Efeito do pH; Eletrodeposição. ELECTROCHEMICAL AND MORPHOLOGICAL CHARACTERIZATION OF NI-FE ALLOYS OBTAINED FROM SULFATE SOLUTIONS AbstractThe behavior of NiFe alloys has been the object of intense research due to its wide industrial application. Electrodeposition is one of the most used processes for producing these alloy films owing to its low cost and capability to recover complex geometries. Parameters of the process such as pH, current density, and bath composition can affect the kinetic of deposition as well as the morphology and structure of the resulting deposits. The aim of the present work is to study the effect of pH solution on the deposition kinetics, composition and morphology of the films. The polarization curves and chemical analysis show two major regions. The first one reflects the H + reduction. Increasing polarization makes the current to vary sharply with potential. High efficiency on metal electrodeposition is observed in this part of the curves. The morphology of the films changes according to the pH solution. At pH 5 the deposits are smooth and compact. At lower pH (pH 1) cracks are observed throughout the surface.

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The Anomalous Codeposition of Iron-Nickel Alloys

Cited by 380 publications

References 3 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

Mechanism of Anomalous Type Electrodeposition of Fe-Ni Alloys from Sulfate Solutions

CARACTERIZAÇÃO ELETROQUÍMICA E MORFOLÓGICA DE LIGAS Ni-Fe OBTIDAS EM SOLUÇÕES DE SULFATO

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