Preparation and characterisation of nanocrystalline cobalt–phosphorus coatings reinforced with carbon nanotubes

Abstract

Nanocrystalline cobalt–phosphorus–carbon nanotube (CNT) composite coatings on stainless steel substrates with various contents of phosphorus were prepared by a pulse electrodeposition technique involving cobalt plating bath dispersed with CNTs. Microhardness, potentiodynamic polarisation and scanning electron microscopy (SEM) studies were used to characterise Co–P and Co–P–CNT composite coatings. The microhardness of Co–P–CNT coatings is found higher than that of Co–P coating. With the increase in phosphorus content, the microhardness values for the heat treated coatings increased almost twice when compared to that of the as deposited coatings. The effects of various contents of phosphorus and CNTs on the corrosion resistance were investigated, and it was found that nanocrystalline Co–P composite coatings exhibit better corrosion resistance than Co–P–CNT coatings.