<p class="AMSmaintext">Currently, Ni-Cr coatings are widely used in a number of important applications due to their excellent properties. In this study, Ni-Cr alloys were electrodeposited from citrate bath onto Cu substrates by using different values of applied current densities. The effects of plating deposition current density on morphological and structural characterization of Ni-Cr electrodeposited coatings were investigated by means of scanning electron microscopy (SEM) and X-ray diffraction (XRD). Microhardness of the coatings is also evaluated using Vickers’s microhardness. Potentio-dynamic polarization and electrochemical impedance spectroscopy (EIS) tests in 3.5wt % NaCl solution were used to evaluate corrosion résistance of Ni-Cr coatings. The results showed that the surface morphology of the all coatings contained micro cracks and pores. XRD patterns indicate the formation of Ni-Cr and Cr₃Ni₂ phases. Microhardness measurements show that all Ni-Cr samples are hardener than copper substrate. Electrochemical tests show that 3 A/dm² is an optimal value of applied current density in the sense of the least value of E_corr and the best charge transfer resistance R_p.</p>

Purpose Because of its wide applications in the industry, the electrodeposition of Ni/Mo as corrosion barrier and decorative coating took the attention of numerous researchers. This paper aims to study the effect of electroplating current density on different characteristics of Ni/Mo alloy coatings, especially on the morphology and electrochemical comportment in 3.5 per cent NaCl corrosion medium. Design/methodology/approach In this paper, the authors have used electrodeposition technique to codeposite molybdenum particles in nickel matrix as protective coating against corrosion attacks, in addition to test the intensification of hydrogen reaction of this alloy coatings using EIS technique. Findings Ni-Mo alloy coating is well adherent to the substrate. The deposited Ni-Mo was observed to be fissured and porous in morphology. The main phases identified in different exposed coatings are MoNi4, Ni3Mo and Mo1.24Ni0.76. The effect of applied current density on electrochemical properties was studied. Inhibitory efficiency of gum arabic was controlled by the electroplating current density. Originality/value In this paper, the authors report on the presence of Mo particles in Ni matrix also the effect of electroplating current density on different properties of alloy coatings Ni/Mo. This is significant because it reports on the effect of current density on Ni/Mo electrodeposited at economic conditions like low temperature and moderate pH. Moreover, this paper gives a solution to the corrosion of crude oil desalter by using Ni-Mo coatings and then injecting a small amount of gum arabic in the oil pipeline before dissalement which gives long life to the reactor.