Microstructure, electrochemical corrosion and corrosion mechanism of electroplated Ni-W alloy coating by DFT calculation

A Ni-W alloy coating with a thickness of 5 mu m was electroplated on N80 steel, and its electrochemical performance in a 3.5% NaCl solution was investigated. The atomic models of passive films and corrosion mechanism were analysed with the density functional theory calculation. The results show that the electroplated Ni-W alloy coating is composed of W atoms in the Ni lattice, and its surface roughness and particle size are 66.1 and 640.4 nm, respectively. The corrosion current density of Ni-W coating is lower than that of the substrate, indicating better corrosion resistance, while the corrosion potential is opposite, which is more passive than the substrate. The total impedance of Ni-W coating is higher than that of the substrate, which is attributed to the formation of NiO passive film during the corrosion process. On a d & eacute;pos & eacute; par galvanoplastie un rev & ecirc;tement en alliage Ni-W d'une & eacute;paisseur de 5 mu m sur l'acier N80 et l'on a examin & eacute; ses performances & eacute;lectrochimiques dans une solution de NaCl & agrave; 3.5%. On a analys & eacute; les mod & egrave;les atomiques des films passifs et le m & eacute;canisme de corrosion au moyen du calcul de la th & eacute;orie fonctionnelle de la densit & eacute;. Les r & eacute;sultats montrent que le rev & ecirc;tement & eacute;lectrolytique en alliage Ni-W est compos & eacute; d'atomes de W dans le r & eacute;seau de Ni et que sa rugosit & eacute; de surface et sa taille de particules sont respectivement de 66.1 et 640.4 nm. La densit & eacute; de courant de corrosion du rev & ecirc;tement en Ni-W est inf & eacute;rieure & agrave; celle du substrat, indiquant une meilleure r & eacute;sistance & agrave; la corrosion, alors que le potentiel de corrosion est & agrave; l'oppos & eacute;, ce qui est plus passif que le substrat. L'imp & eacute;dance totale du rev & ecirc;tement en Ni-W est sup & eacute;rieure & agrave; celle du substrat, ce qui est attribu & eacute; & agrave; la formation d'un film passif de NiO pendant le proc & eacute;d & eacute; de corrosion.