Insight into the Role and Its Mechanism of Polyacrylamide as an Additive in Sulfate Electrolytes for Nanocrystalline Zinc Electrodeposition

Abstract

Electrodeposition of nanocrystalline zinc coating is greatly significant in improving the mechanism, wear and corrosion properties of conventional coarse-grained zinc coating and its formation is usually by the synergetic effect of two or more additives on electrodeposition reaction. However, the multicomponent additives not only make the electrolytes complicate and unstable, but also difficult to analyze the effect mechanism of each additive on electrodeposition of nanocrystalline zinc coating. In this study, nanocrystalline zinc coating is electrodeposited from a simple sulfate bath with polyacrylamide as the only additive. The influence and effect mechanism of polyacrylamide on electrodeposition of nanocrystalline zinc coating are investigated. It is found that the addition of polyacrylamide does not change the instantaneous nucleation mechanism with three-dimensional diffusion-controlled growth nucleation of zinc, however an increase in the zinc deposition potential is observed in the presence of polyacrylamide compared with electrodeposition of zinc coating from the additive-free bath. The zinc deposition overpotential increase is due to the absorption of polyacrylamide on the surface of the electrode, specifically the synergistic adsorption of its polymer chain and amine group, which is beneficial for increasing the free energy to form new nuclei, thereby results in a higher nucleation rate and smaller grain size. Electrodeposition of zinc coating as a common, practical and low cost surface modification technology has been widely employed in field of protection of steel against corrosion. However, the poor mechanical, tribological and electrochemical properties of conventional zinc electrodeposits increase the probability of damage and thus, reduce the life of the coating, as well as lead to a wasted of zinc. Therefore, many efforts have been made in order to improve its properties, such as chemical passivation, heat treatment, superhydrophobic treatment and nano-electrodeposition technologies.1-4 Among these methods, nano-electrodeposition is undoubtedly the most promising alternative for conventional electrodeposition technology. This is because the nano-electrodepositon doesn't require post-processing treatment compared with others surface treatment methods. Previous researches have also demonstrated that the nanohardness increased to about 3 times when the grain size of coarse-grained zinc coatings was reduced from micro to nano scales, and the wear rate of nanocrystalline zinc coating was found to be about 96% lower than that of coarsegrained zinc coating. 5 The corrosion rate of the nanocrystalline zinc coating is less than 1/2 of that of the coarse-grained zinc coating in NaCl and NaOH corrosion mediums. 6,7 So far, several related works about electrodeposition of nanocrystalline zinc coatings were reported. Such as Ramanauskas et al. 8 electrodeposited the nanocrystalline zinc coatings from an alkaline cyanide-free solution in the presence of organic additives by pulse electrodeposition, with ...

Recent Progress on Zn Anodes for Advanced Aqueous Zinc‐Ion Batteries

“…High polymers, represented by polyacrylamide (PAM), [ 48a,159 ] polyethylene glycol (PEG), [ 160 ] etc., also have the characteristics of adsorption. The special polymer long chains can provide selective adsorption sites for Zn 2+ and facilitate a homogeneous distribution of Zn 2+ on the anode surface, to achieve more stable zinc deposition (Figure 16c).…”

Rechargeable Aqueous Zinc‐Ion Batteries with Mild Electrolytes: A Comprehensive Review

“…As a typical low-cost polymer containing ketone unit, polyacrylamide (PAM) had been verified an effective electrolyte additive to suppress the formation of dendrites during the electrodeposited Zn. [215] Density functional theory (DFT) calculations that the acyl groups on PAM can selectively adsorb Zn 2 + ions, enabling the transfer of Zn 2 + ions along the polymer chains. Based on this understanding, Zhang and Wang et al [216] further developed a synergistic method combining the Cu-Zn solid solution interface on a copper mesh skeleton with good zinc affinity and a polyacrylamide electrolyte additive to modify the zinc anode, which can greatly reduce the over-potential of the zinc nucleation and increase the stability of zinc deposition.…”

“…Generally, most of these brighteners are ketone or aromatic aldehyde compounds. As a typical low‐cost polymer containing ketone unit, polyacrylamide (PAM) had been verified an effective electrolyte additive to suppress the formation of dendrites during the electrodeposited Zn . Density functional theory (DFT) calculations that the acyl groups on PAM can selectively adsorb Zn 2+ ions, enabling the transfer of Zn 2+ ions along the polymer chains.…”

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“…The electrodeposit zinc is based on its appropriate cathodic and barrier defensive properties. By including the eighth group element, such as nickel, iron and cobalt, into the system, the zinc coatings made in this way can greatly enhance the anti-corrosion properties [4,5].…”