INTRODUCTION

EXPERIMENTAL

RESULTS AND DISCUSSION

KINETIC STUDIES

CONCLUSIONS

REFERENCES

Abstract

The present paper aims to compare the corrosion protection performance of electrodeposited Ni‒P with Ni–P–C nanocomposite coatings in 3.5 wt % NaCl solution in order to assess the influence of carbon nanoparticles on corrosion behavior of these coatings, by the potentiodynamic polarisation Tafel curves and electrochemical impedance spectroscopic (EIS) techniques. The effect of heat treatment on the coatings performance was also studied. The results revealed that heat treated Ni–P–C nanocomposite coating in air at 673 K significantly improved resistance to corrosion compared with Ni–P coatings. This behavior was related to incorporation of carbon nanoparticles into Ni–P matrix using in-situ electrochemical reduction of L-lysine, which shift the corrosion potential (Ecorr) positively, also the corrosion current density (Icorr) and the double layer capacitance (Cdl) values decrease, the charge transfer resistance (Rct) and efficiencies of inhibition (IE, %) increase, indicating improvement in the corrosion resistance in seawater environment. Microstructure, phase change and chemical composition of the prepared coatings were studied using scanning electron microscopy (SEM), X-ray diffraction (XRD) and elemental microanalysis (EDX), respectively.

INTRODUCTION

Electrodeposited composite coatings based on a Ni–P alloy matrix containing different fine particles of nonmetallic, ceramic or polymer compounds [1‒۱۰] have attracted attention in many industrial fields due to their good mechanical, chemical and electrocatalytic properties including enhanced wear resistance combined with a good corrosion resistance and especially high electrocatalytic activity for hydrogen evolution reaction (HER) in chlor-alkali industries and water electrolysis [11–۱۷], when compared to pure nickel coatings. Ni–P coating with phosphorus content over 9 wt % are considered amorphous and possesses excellent mechanical properties such as corrosion resistance [18, 19]. This protective film can be deposited by electroplating and electroless plating onto a metallic or nonmetallic substrate to prevent attack by hostile environments [20].