Eletrodeposição de uma camada multielementar de Ni-Co-Cu-Fe : efeito da densidade de corrente

Abstract

The electroplating deposition of multielementar alloys has aroused great interest in the research and in various market segments, such as in the aeronautical, naval, automotive, petrochemical industries, among other applications, due to its exceptional properties, such as high resistance to corrosion, wear, mechanical resistance, high fatigue strength, magnetic properties and heat softening resistance. These properties are obtained by the synergistic response based on the concept of high entropy of mixing of multielement systems, where the deposited layer is composed by a solid substitutional solution with body-centered cubic (BCC), face-centered cubic (FCC), and hexagonal compact structures. The purpose of this work is to investigate the effects of current density changes in the electrodeposition layers of Ni-Co-Cu-Fe alloys with equiatomic compositions. The electro-deposited alloys were obtained in a solution of 0.1mol.dm-3 of NiSO4.6H2O, 0.1mol.dm-3 of CoSO4.7H2O, 0.02mol.dm-3 FeSO4.7H2O, 0.01mol.dm-3 CuSO4.5H2O (bath 1) and 0.1mol.dm-3 of NiSO4.6H2O, 0.1mol.dm-3 of CoSO4.7H2O, 0.1mol.dm-3 FeSO4.7H2O, 0.1mol.dm-3 CuSO4.5H2O, 0.1mol.dm-3 MnSO4.H2O (bath 2), all at pH 4. Electrodeposition was carried out under galvanostatic control, with current densities changing from 10 mA.cm-2 to 65 mA.cm-2 for 30 min at room temperature. All coatings were deposited on SAE 1010 carbon steel subtracts with area of 1.0 cm2. The corrosion behavior and the microstructure were investigated by Scanning Electron Microscopy, Energy Dispersive Spectroscopy and X-Ray Diffraction. The electrodeposited coatings of Ni-Co-Cu-Fe showed better anticorrosive performance in NaCl 3.5 mol.dm-3, which were obtained using density 50 mA.dm-3 current density. The morphological analysis showed that the Ni-Co-Cu-Fe layers are homogeneous compared to the Mn-Fe-Ni-Co-Cu alloy. In addition, it was found that the lower current density used improved grain refinement, resulting in a higher deposition of cobalt in the coating, around 59.1 at%. The X-ray diffraction scans showed that the Fe-Ni-Co-Cu layers structure is predominantly BCC.