Cracking of electroless Ni-P coatings due to lower toughness hinder its application in various service conditions, and in turn demands improved toughness and corrosion resistance using a ternary coating matrix. On the other hand, graphene is known for its higher hardness, impermeability; so, was selected as a candidate for ternary coating systems. In this research, 1 wt. % graphene suspension after Raman Spectroscopic checks was added into electroless Ni-P plating bath in various concentrations to produce three different compositions of Ni-P-G (graphene) coatings. Micro-structural and surface attributes were studied using scanning electron microscope and laser confocal microscope, respectively. Scratch and indentation behaviors of substrate and coatings were investigated using UMT Scratch tester and Hertzian type Indenter. Corrosion resistance results from potentiodynamic testing of ternary coatings were compared with that for substrate steel and as-plated Ni-P coating. Graphene incorporation in Ni-P coating matrix improved the Vickers micro-hardness as well as wear resistance. Also, graphene induced Ni-P coating exhibited increased corrosion resistance and toughness.
Plant assets for hydrocarbon and chemical industries are prone to deterioration due to various damage mechanisms that arise from operating conditions, upset conditions, environmental factors, material defects as well as neighborhood-driven events.1–2 Corrosion is a key degradation that jeopardizes the reliability and even retards the operating performance of assets due to adjusted IOW (integrity operating windows). On an average, spending of industrialized economies for corrosion management efforts are reported to be 3.4–6.1% of overall GDP.3–4 Various efforts of corrosion management include (but not limited to) materials upgrades, chemical inhibitions, cathodic protections, research and development and protective coatings etc. Moreover, corrosion allowances are kept in the assets during design, that incur the increase in capital cost of the operating facilities.
Coating is an effective measure to protect the metal's surface and known for versatility, ease of maintenance and various compositions specific to service. Various epoxy coating systems are known for hydrocarbon applications till date; that include but not limited to inorganic Zn epoxy, glass flake epoxy, coal tar epoxy, phenolic epoxy etc. Also, various techniques for coatings are known such as TS (thermally spraying), friction-surfacing, electroplating and electroless etc. Electroless Ni-P coatings have higher hardness as well as significant corrosion resistance due to the absence of grain boundaries pertaining to its amorphous microstructure. Also, these coatings have excellent adhesion properties even for sharp contours and can potentially be used for various applications. On the other hand, it's quite brittle and can crack especially in the event of scratch or impact loadings. 5–7
