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.

Corrosion behaviour of compositionally modulated nanocrystalline Ni–W coatings

“…In addition to corrosion resistance which requires sealing of cracks from the underlying substrate, there is substantial fatigue debt of component due to inherent tensile residual stresses in Cr coating [8]. These coatings possess low thermal stability [9]. Owing to aforementioned reasons, an intensive effort is under way globally to identify a suitable replacement coating [10,11].…”

Optimising parameters for galvanostatic polyaniline coating on nanostructured bainitic steel

“…16,17,[21][22][23] Conducting polymer coating on metals can be performed using chemical or electrochemical method. [24][25][26][27][28][29][30] Literature suggest the electrochemical techniques such as cyclic voltammetry, potentiostatic and galvanostatic methods 21,27,[31][32][33] are more attractive due to the direct synthesis of the coating on metal surface, 30 and the ease to coat complex-shaped components. Among the electrochemical techniques, the galvanostatic method is more suitable for industrial applications for its simple one-step process and easy control of the thickness of the coating.…”

“…Recently, the use of neutral aqueous media such as oxalic acid and sodium salicylate have been studied and have shown promising results on low-carbon steels. [31][32][33][34][35][36] Since the corrosion characteristics of the base material play a significant role on the coating of conducting polymers, it is critical to optimise the process parameters for coating a conducting polymer on nanostructured bainitic steel which has high-carbon content and undergo selective dissolution in chloride-containing solution. In this study, PANI was galvanostatically coated on nanostructured bainitic steel and the corrosion behaviour of the coated steel was evaluated using electrochemical techniques in a chloride-containing solution.…”