Structural Analysis of Thin Ni-P Layers

The deposition mechanism by autocatalytic reduction method is a chemical one, which does not lead to structures as shown in the Ni-P balance diagram. In the experiments of the present work, Ni-P layers were made deposited on thin steel strip with low carbon content. By optical microscopy and scanning electron microscopy by (SEM) it was analyzed the appearance and surface morphology of the deposited layers depending on the content of phosphorus and working parameters (temperature, pH, stirring speed). The layer structure was analyzed in the cross section and on the break surface. The analysis results show that thin coatings of Ni-P have a surface topography that follows faithfully the steel support. Depending on the content of phosphorus, on the layer surface of low phosphorus content, spherical particles of different sizes can be seen while high and average phosphorus content coatings feature a smooth surface with nanometer-sized grains. Analysis of the cut-off /break section of the Ni-P layer structure, show a more or less porous structure depending on the stirring speed and pH level.