Effects of electrolyte concentration and current density on the properties of electro-deposited NiFeW alloy coatings

NiWP alloy coatings were prepared by electrodeposition, and the effects of ferrous chloride ( $$\hbox {FeCl}₂)$$ , sodium tungstate ( $$\hbox {Na}₂\hbox {WO}₄)$$ and current density ( $$D_{\mathrm{K}}$$ ) on the properties of the coatings were studied. The results show that upon increasing the concentration of $$\hbox {FeCl}₂$$ , initially the Fe content of the coating increased and then tended to be stable; the deposition rate and microhardness of coating decreased when the cathodic current efficiency ( $$\eta $$ ) initially increased and then decreased; and for a $$\hbox {FeCl}₂$$ concentration of $$3.6\, \hbox {g\,l}^-1$$ , the cathodic current efficiency reached its maximum of 74.23%. Upon increasing the concentration of $$\hbox {Na}₂\hbox {WO}₄$$ , the W content and microhardness of the coatings increased; the deposition rate and the cathode current efficiency initially increased and then decreased. The cathodic current efficiency reached the maximum value of 70.33% with a $$\hbox {Na}₂\hbox {WO}₄$$ concentration of 50 g $$\hbox {l}^-1$$ , whereas the deposition rate is maximum at 8.67 $$\upmu \hbox {m}\,\hbox {h}^-1$$ with a $$\hbox {Na}₂\hbox {WO}₄$$ concentration of $$40\, \hbox {g\,l}^-1$$ . Upon increasing the $$D_{\mathrm{K}}$$ , the deposition rate, microhardness, Fe and W content of the coatings increased, the cathodic current efficiency increases first increased and then decreased. When $$D_{\mathrm{K}}$$ was 4 A dm $$^-2$$ , the current efficiency reached the maximum of 73.64%.