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Acidic Bath
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G. Trejo – One of the best experts on this subject based on the ideXlab platform.
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characterization of the corrosion products of electrodeposited zn zn co and zn mn alloys coatings
Corrosion Science, 2009Co-Authors: Z.i. Ortiz, Y. Meas, P Diazarista, R Ortegaborges, G. TrejoAbstract:Abstract The morphology, composition, phase composition and corrosion products of coatings of pure Zn (obtained from two types of electrolytic Bath: an Acidic Bath (Zn acid ) and a cyanide-free alkaline Bath (Zn alkaline )) and of Zn–Mn and Zn–Co alloys on steel substrates were studied. To achieve this, diverse techniques were used, including polarization curves, atomic force microscopy (AFM), scanning electron microscopy (SEM), glow discharge spectroscopy (GDS), X-ray diffraction (XRD), and the salt spray test. In the salt spray test, the exposure time required for the coatings to exhibit red corrosion (associated with the oxidation of steel) decreased in the following order: Zn–Mn (432h) > Zn–Co (429h) > Zn alkaline(298h) > Zn acid(216h) . The shorter exposure times required for corrosion of the pure Zn coatings are related to the coating composition and the crystallographic structure. Analysis of the corrosion products disclosed that Zn 5 (OH) 8 Cl 2 ·H 2 O was a corrosion product of all of the coatings tested. However, the formation of oxides of manganese (MnO, Mn 0.98 O 2 , Mn 5 O 8 ) in the Zn–Mn coating, and the formation of the hydroxide Zn 2 Co 3 (OH) 10 ·2H 2 O in the Zn–Co coating, produced more compact and stable passive layers, with lower dissolution rates.
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Electrochemical and AFM study of Zn electrodeposition in the presence of benzylideneacetone in a chloride-based Acidic Bath
Journal of Applied Electrochemistry, 2005Co-Authors: P. Díaz-arista, R. Ortega, Y. Meas, G. TrejoAbstract:The influence of benzylideneacetone (BDA) on the mechanism of zinc deposition and nucleation was studied by voltammetry, chronoamperometry and atomic force microscopy (AFM). The addition of BDA to the electrolyte solution partially inhibited (97%) the reduction of zinc at the potential E = −1.15 vs SCE/V, giving rise to an increase in the overpotential for the discharge of the metal ion. This leads to the existence of two reduction processes with different energies that involve the same species, ZnCl _4 ^2- . Analysis of chronoamperograms obtained in the absence and presence of BDA indicates that distinct nucleation mechanisms are involved during the initial stages of Zn deposition. In the absence of BDA, the transients are consistent with the model of 3D diffusion-controlled nucleation. In the presence of BDA, the transients exhibit a more complex form involving two growth processes. The first process, which occurs at short times, is explained in terms of a combination of three simultaneous nucleation processes: 2D progressive, 2D instantaneous, and 3D progressive nucleation, each limited by the incorporation of adatoms. The second process, which occurs at longer times, involves the three processes that occur at short times in conjunction with a principal contribution from a diffusion-controlled 3D nucleation mechanism. AFM imaging shows that the morphology of the deposited zinc depends on the applied electrode potential.
Z.i. Ortiz – One of the best experts on this subject based on the ideXlab platform.
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characterization of the corrosion products of electrodeposited zn zn co and zn mn alloys coatings
Corrosion Science, 2009Co-Authors: Z.i. Ortiz, Y. Meas, P Diazarista, R Ortegaborges, G. TrejoAbstract:Abstract The morphology, composition, phase composition and corrosion products of coatings of pure Zn (obtained from two types of electrolytic Bath: an Acidic Bath (Zn acid ) and a cyanide-free alkaline Bath (Zn alkaline )) and of Zn–Mn and Zn–Co alloys on steel substrates were studied. To achieve this, diverse techniques were used, including polarization curves, atomic force microscopy (AFM), scanning electron microscopy (SEM), glow discharge spectroscopy (GDS), X-ray diffraction (XRD), and the salt spray test. In the salt spray test, the exposure time required for the coatings to exhibit red corrosion (associated with the oxidation of steel) decreased in the following order: Zn–Mn (432h) > Zn–Co (429h) > Zn alkaline(298h) > Zn acid(216h) . The shorter exposure times required for corrosion of the pure Zn coatings are related to the coating composition and the crystallographic structure. Analysis of the corrosion products disclosed that Zn 5 (OH) 8 Cl 2 ·H 2 O was a corrosion product of all of the coatings tested. However, the formation of oxides of manganese (MnO, Mn 0.98 O 2 , Mn 5 O 8 ) in the Zn–Mn coating, and the formation of the hydroxide Zn 2 Co 3 (OH) 10 ·2H 2 O in the Zn–Co coating, produced more compact and stable passive layers, with lower dissolution rates.
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Electrodeposition and characterization of Zn-Mn alloy coatings obtained from a chloride-based Acidic Bath containing ammonium thiocyanate as an additive
Surface and Coatings Technology, 2009Co-Authors: P. Díaz-arista, Z.i. Ortiz, H. Ruiz, R. Ortega, Yunny Meas, Gabriel TrejoAbstract:Abstract The electrodeposition of Zn–Mn alloys was performed using a chloride-based Acidic Bath containing ammonium thiocyanate (NH4SCN) as an additive. An electrochemical study using cyclic voltammetry (CV), performed for each of the metal ions (Zn(II) and Mn(II)), showed that neither metal ion forms complexes with NH3, and that Mn(II) but not Zn(II) forms complexes with SCN−. The influence of NH4SCN on the morphology, composition and crystallographic structure of the electrodeposited Zn–Mn alloys was studied using scanning electron microscopy (SEM), glow discharge spectroscopy (GDS) and X-ray diffraction (XRD). The results show that the presence of NH4SCN in the solution induces an increase in the Mn content of the alloy, from 3% in the Zn–Mn alloy obtained in the absence of additive to 6.2% in the alloy obtained in the presence of additive. In addition, the presence of NH4SCN favors the formation of coatings comprised of a mixture of e-phase Zn–Mn(002) + α-phase Zn–Mn(111) alloys. These coatings were compact and smooth and exhibited a lower corrosion rate compared to the coatings obtained in the absence of NH4SCN, which where comprised of a mixture of Zn, e-phase Zn–Mn and α-phase Zn–Mn alloys.
P. Díaz-arista – One of the best experts on this subject based on the ideXlab platform.
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Electrodeposition and characterization of Zn-Mn alloy coatings obtained from a chloride-based Acidic Bath containing ammonium thiocyanate as an additive
Surface and Coatings Technology, 2009Co-Authors: P. Díaz-arista, Z.i. Ortiz, H. Ruiz, R. Ortega, Yunny Meas, Gabriel TrejoAbstract:Abstract The electrodeposition of Zn–Mn alloys was performed using a chloride-based Acidic Bath containing ammonium thiocyanate (NH4SCN) as an additive. An electrochemical study using cyclic voltammetry (CV), performed for each of the metal ions (Zn(II) and Mn(II)), showed that neither metal ion forms complexes with NH3, and that Mn(II) but not Zn(II) forms complexes with SCN−. The influence of NH4SCN on the morphology, composition and crystallographic structure of the electrodeposited Zn–Mn alloys was studied using scanning electron microscopy (SEM), glow discharge spectroscopy (GDS) and X-ray diffraction (XRD). The results show that the presence of NH4SCN in the solution induces an increase in the Mn content of the alloy, from 3% in the Zn–Mn alloy obtained in the absence of additive to 6.2% in the alloy obtained in the presence of additive. In addition, the presence of NH4SCN favors the formation of coatings comprised of a mixture of e-phase Zn–Mn(002) + α-phase Zn–Mn(111) alloys. These coatings were compact and smooth and exhibited a lower corrosion rate compared to the coatings obtained in the absence of NH4SCN, which where comprised of a mixture of Zn, e-phase Zn–Mn and α-phase Zn–Mn alloys.
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Electrochemical and AFM study of Zn electrodeposition in the presence of benzylideneacetone in a chloride-based Acidic Bath
Journal of Applied Electrochemistry, 2005Co-Authors: P. Díaz-arista, R. Ortega, Y. Meas, G. TrejoAbstract:The influence of benzylideneacetone (BDA) on the mechanism of zinc deposition and nucleation was studied by voltammetry, chronoamperometry and atomic force microscopy (AFM). The addition of BDA to the electrolyte solution partially inhibited (97%) the reduction of zinc at the potential E = −1.15 vs SCE/V, giving rise to an increase in the overpotential for the discharge of the metal ion. This leads to the existence of two reduction processes with different energies that involve the same species, ZnCl _4 ^2- . Analysis of chronoamperograms obtained in the absence and presence of BDA indicates that distinct nucleation mechanisms are involved during the initial stages of Zn deposition. In the absence of BDA, the transients are consistent with the model of 3D diffusion-controlled nucleation. In the presence of BDA, the transients exhibit a more complex form involving two growth processes. The first process, which occurs at short times, is explained in terms of a combination of three simultaneous nucleation processes: 2D progressive, 2D instantaneous, and 3D progressive nucleation, each limited by the incorporation of adatoms. The second process, which occurs at longer times, involves the three processes that occur at short times in conjunction with a principal contribution from a diffusion-controlled 3D nucleation mechanism. AFM imaging shows that the morphology of the deposited zinc depends on the applied electrode potential.