Investigation of nucleation mechanism and surface morphology of the crystallites in zinc-cobalt alloy coating

  • Fig. 1: Hull cell experimental results: (a) Key, Influence of (b) Brightener (TG) (c) Zinc Sulphate (d) Cobalt Chloride (e) Sodium sulphate (f) Boric acid (g) Cetyl trimethyl ammonium bromide (CTAB) (h) pH (i) Temperature (j) Current

In present investigation, a new brightener was synthesized by condensation of 3, 4, 5-Trimethoxy benzaldehyde and Glycine (TG). Hull cell experiments were conducted to optimize the plating bath components and operating parameters. To examine the influence of TG on nucleation mechanism of Zn-Co alloy electrodeposition, cyclic voltammetry and chronoamperometry study was carried out. Schariffker and Hills model was used to analyze current transients, which in presence of TG confirmed instantaneous nucleation. Corrosion studies were done using potentiodynamic polarization and electrochemical impedance spectroscopic technique, in 3.5 wt. % NaCl for bright and dull zinc-cobalt alloy coatings. Phase structure, surface morphology and brightness of the deposit were characterized by X-ray diffraction analysis, scanning electron microscopy and reflectance studies. These studies revealed the role of TG in modifying the nucleation mechanism and surface morphology of zinc-cobalt alloy crystallites and thereby producing a bright corrosion resistant Zn-Co alloy coating on mild steel substrate.


The need for digitalisation in electroplating - How digital approaches can help to optimize the electrodeposition of chromium from trivalent electrolytes

  • Fig. 1: Example of an ontology for the description of the electrodeposition of chromium and the characterization of the layer properties. The scheme contains optimization loops for the chromium deposition process by ML and simulation based modelling
    Fig. 1: Example of an ontology for the description of the electrodeposition of chromium and the characterization of the layer properties. The scheme contains optimization loops for the chromium deposition process by ML and simulation based modelling

In order to make material design processes more efficient in the future, the underlying multidimensional process parameter spaces must be systematically explored using digitalisation techniques such as machine learning (ML) and digital simulation. In this paper we shortly review essential concepts for the digitalisation of electrodeposition processes with a special focus on chromium plating from trivalent electrolytes.


Influence of wet surface pretreatment on the electroless metallization of stereolithography resins

In the present paper, the influence of different wet pretreatment routes on the final quality of electroless layers plated on stereolithography resins is investigated. Two pretreatment methods, acidic and alkaline, are employed. Acidic etching is unable to provide acceptable results in terms of surface quality. On the contrary, alkaline etching guarantees a bright copper surface coupled with a level of adhesion high enough to pass a standard peel test. ATR FT-IR is employed to investigate the chemical reactions occurring on the resins during the pretreatment, evidencing a major role of the ester hydrolysis process on the depolymerization of the material and on the formation of new functional groups on the surface. Resin hydrolysis is linked with increase in surface roughness and wettability, parameters that strongly determine final metal adhesion. The combination of ATR FT-IT, contact angle and roughness measurement constitutes a possible combined methodology to follow the evolution of surface pretreatment on different stereolithography resins.


Electrochemical deposition of silicon from organic electrolytes

  • Fig. 3: Linear sweep voltammograms of 0.5 M SiCl4 in propylene carbonate based electrolyte (ν = 10 mV s-1). Inset: SEM micrographs of the resulting layers from the deposition at -1.7 V for 2 h on copper (a) and at -1.88 V for 2 h on nickel (b)

Electrochemical reduction of silicon from SiCl4 in 1-butyl-1-metyl-pyrrolidinium bis(trifluoromethylsulfonyl)imide [BMP][TFSI] and in propylene carbonate (PC) with SiCl4 as a precursor is performed at room temperature. The process is studied by means of Linear Sweep Voltammetry and chronoamperometry. The results exhibit considerable differences during the silicon deposition for copper and nickel. Scanning Electron Microscopy (SEM) of the layers shows a rough surface morphology. The composition of Si deposit is confirmed by Energy Dispersive X-ray analysis (EDX). Furthermore, the deposition of silicon onto TiO2 nanotubes is discussed. In conclusion, a method of recycling the used ionic liquid by a simple extraction procedure is presented.


Electrochemical studies of the bright Zn-Ni alloy electrodeposit from acid sulphate bath

  • Fig. 3: Non-dimensional (I / Imax)2 versus t / tmax plot for electrodeposition of zinc-nickel alloy coating obtained from zinc-nickel bath: 0.5M ZnSO4 + 0.1M NiSO4 + 0.29M Na2SO4 + 0.26M H3BO3 + 0.01M CTAB and at pH = 3 (A) in absence and (B) in presence of 40 mlL-1 VC

The condensation product of Vanillin and Cysteine Hydrochloride (VC) was used as an additive for the electrodeposition of Zn-Ni alloy on mild steel substrate. The bath constituents and operating conditions were optimized by Hull cell experiments. The electrochemical behaviour and nucleation mechanism was studied using cyclicvoltammetry and chronoamperometric techniques. The electrochemical studies revealed that electrocrystallisation process of zincnickel alloy coating was governed by three-dimensional (3D) nucleation process, controlled by diffusion. The model of Schariffker and Hills was used to analyze the current transients and it revealed that, in bright zinc-nickel alloy coating, the electrocrystallization process is regulated by instantaneous nucleation mechanism. The electrochemical impedance spectroscopy and Tafel polarization studies were used to study corrosion nature of Zn-Ni electrodeposits. Corrosion studies showed an improved corrosion resistant nature of bright Zn-Ni alloy coatings on mild steel substrate. The scanning electron microscopy (SEM) and X-ray diffraction (XRD) studies depicted smooth, compact and fine-grained structure of Zn-Ni electrodeposit in presence of VC, in plating bath solution.