Effect of sodium diisopropylnaphthalene sulfonate on Zn-Mn alloys electrodeposition
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ORIGINAL PAPER
Effect of sodium diisopropylnaphthalene sulfonate on Zn-Mn alloys electrodeposition N. Loukil 1 & M. Feki 1 Received: 27 May 2020 / Revised: 23 August 2020 / Accepted: 25 August 2020 # Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract A novel additive sodium diisopropylnaphthalene sulfonate (SDIPNS) was investigated in Zn-Mn electrodeposition on steel from chloride bath. To this end, cyclic voltammetry was performed in absence and presence of SDIPNS to study different electrochemical systems. Electrochemical data showed that SDIPNS increases Zn deposition overpotential, resulting from strong adsorption of SDIPNS molecules on the cathode surface. The effects of scan rate, switching potentials on the electrochemical behavior of Zn-Mn co-deposition were investigated. The variation of scan rate reveals that the Zn-Mn co-deposition is associated with charge transfer coupled with the mass transfer. SDIPNS concentration was investigated with regard to the Mn content in the final coatings. The chemical composition result showed that Mn-rich deposits, containing 20 wt.% of Mn, are successfully deposited under low cathodic potential (E = − 1.52 V vs. Ag/AgCl). The surface characterization of Zn-Mn coatings was explored by scanning electron microscopy (SEM). The presence of SDIPNS in the electrolytic bath permits to obtain compact, well adherent, and fined grain Mn-rich alloys. Keywords Zn-Mn alloys . Co-deposition . Adsorption . Mn content . Morphology
Introduction Zinc coatings are commonly used to protect sacrificially steel from corrosion [1–3]. However, zinc itself undergoes corrosion, which probably decreases the performance and stability of the coating. To improve its performance in a harsh environment, alloying Zn with other metals, namely Co, Ni, Fe, and Mn, is an alternative way to generate advanced alloys with better corrosion properties [3]. Zn-Mn coatings have attracted much attention since these alloys exhibit higher corrosion protection compared with pure zinc and other zinc alloys [4–12]. It has been found that Zn-Mn deposits show the highest protective ability if the Mn content is ranging from 10 [13–16] to 40% [6, 10, 11].
* N. Loukil [email protected] M. Feki [email protected] 1
Laboratoire de Génie des Matériaux et Environnement (LGME), ENIS, P.B. 1173-3038, Université de Sfax, Sfax, Tunisie
Mn-rich deposits obtained from aqueous baths imply significant challenges. As a matter of fact, the standard electrode potentials of Zn2+/Zn and Mn2+/Mn couples significantly differ − 0.76 V/SHE and − 1.18 V/SHE, respectively. These two deposition potentials are more negative than that of hydrogen ions [1, 16, 17] such that Zn-Mn electrodeposition is undoubtedly accompanied by hydrogen evolution reaction, leading to major drawbacks as low current efficiency and poor adhesion of coatings [16, 19]. Simultaneous reduction of Zn2+ and Mn2+ cations can merely be achieved if their reduction potentials are close [19–23]. It is advisable to note that the reduction potential depends on
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