CREATIVE ADVANCES IN CARBON ALLOTROPE-BASED CORROSION INHIBITOR SYSTEMS.pptx

CREATIVE ADVANCES IN CARBON ALLOTROPE-BASED CORROSION INHIBITOR SYSTEMS

1. CREATIVE ADVANCES IN CARBON ALLOTROPE-BASED CORROSION INHIBITOR SYSTEMS Dr. A. MUSHIRA BANU ASSISTANT PROFESSOR OF CHEMISTRY JAMAL MOHAMED COLLEGE TIRUCHIRAPPALLI - 620020

2. INTRODUCTION Corrosion is highly destructive phenomenon in which metallic materials degrade through the reaction of constituents of surrounding environment. Various industrial processes which involve the implementation of highly acidic solutions greatly constitute in the economic losses of corrosion. Some of commonly employed industrial processes are acid cleaning, acid descaling, acid pickling and oil-well acidification. In these processes highly concentrated acidic solutions are used to remove the surface impurities including rusts and scales. However, along with cleaning the surface impurities, the highly aggressive solution also causes huge loss of metallic component through corrosion. Among the various methods, use of organic compounds containing heteroatoms in the form of polar functional groups such and multiple (double and triple) bonds, is one of the most effective and popular methods of corrosion mitigation. T he recent progress in using nanomaterials as corrosion inhibitors is gaining particular attention. Nanomaterials have extremely larger surface areas as compared to larger-scale materials/chemicals of similar masses. Because of their extremely high surface areas, nanomaterials provide excellent metallic surface coverage and behave as effective anticorrosive materials.

3. Nano-sized carbon allotropes, particularly graphene (G), graphene oxide (GO), single and multi-walled carbon nanotubes (CNTs, SWCNTs, and MWCNTs) and their chemically modified derivatives are widely used in anticorrosive coating formulations. Generally, carbon allotropes acquire nanofiller property and high hydrophobicity which make them ideal anticorrosive materials. Along with various advantages, using carbon allotropes as anticorrosive materials are connected with some specific challenges including un-controlled dispersion in polymer matrixes. Chemical functionalization using covalent and non-covalent methods are widely used to enhance their dispersibility. Magnetic stirring, ultrasonic mixing, ball milling and shear emulsification are also widely used to enhance their dispersibility. Present study describes the covalent and non-covalent functionalization of G, GO, and CNTs and their application as corrosion inhibitors in various coating formulations and aqueous phase. Chemically modified GO shows remarkable solubility/dispersibility in the aqueous electrolytes.

4. ROLE OF NANOTECHNOLOGY AS NEXT GENERATION OF CORROSION INHIBITOR SYSTEMS Pictorial illustration of various modes of interaction between metal surface and functionalized nanomaterials (CNT) The adsorption of the nanomaterials on metallic surface can be divided into two steps. First step involves the transfer of nanomaterials to metal surface from bulk solution and second step involves their adsorption through coordination bonding. Transfer of non-bonding and π - electrons from nanomaterials to metal surface can be termed as donation. Though, metals are already electron rich species, this-type of electron transfer can result into a state of thermodynamical instability because of the inter-electronic repulsion. Therefore, during interaction of nanomaterials, it is also possible that electrons are transferred back into the empty p-orbital of heteroatoms (nanomaterials). This is known as retro (back)- donation. Both donation and retro (back)-donation strengthen each other through a phenomenon known as synergism.

5. EXPERIMENTAL PROCEDURE Our research team demonstrated the corrosion inhibition effect of two functionalized GO namely, aminoazobenzene -GO (AAB-GO) Diaminobenzene-GO (DAB-GO) for mild steel corrosion in acidic solution of 1 M HCl. Both GO composites were synthesized (using modified Hummers method). The Synthesized composites were characterized using FTIR, TEM, XPS, and XRD techniques. Scheme for the synthesis of AAB-GO and DAB-GO is presented in Figure.

6. Schemes for the synthesis of AAB-GO and DAB-GO

7. RESULTS AND DISCUSSION Open circuit potential (OCP) versus time (second) curves analysis suggest that AAB-GO and DAB-GO become effective by adsorbing on the metallic surface using their polar functional groups. Straight OCP vs time curves were observed in the presence of AAB-GO and DAB-GO indicating that they adsorbed on metallic surface by replacing the surface oxide layers. Potentiodynamic study showed that AAB-GO and DAB-GO acted as mixed-type corrosion inhibitors as they became effective by retarding both anodic and cathodic Tafel reactions.

8. AAB-GO and DABGO adsorb at the interface of metal and electrolyte and behave as interface-type corrosion inhibitors. Presence of these composites in corrosive medium increases the magnitude of charge transfer resistance. This observation reveals that AAB-GO and DAB-GO become effective by adsorption mechanism. Adsorption mechanism of corrosion inhibition using AAB-GO and DAB-GO was further supported by SEM study where significant improvement in the morphology of metal surface was observed in their presence. Interaction of AAB and DAB with metallic surface was investigated using DFT based quantum chemical calculations. A good agreement in the results of experimental and computational analyses was observed.

9. CONCLUSION Carbon allotropes, especially graphene (G), GO, CNTs and their derivatives are widely used as anticorrosive coatings because of their large surface area, filler and hydrophobicity properties. T he carbon allotropes, especially graphene (G), GO, CNTs and their derivatives are ideal nano-sized candidates to replace the traditional molecular corrosion inhibitors. Because of their high surface areas, these materials provide excellent surface coverage and protection. In view of this, several reports dealing with the anticorrosive effect of G, GO, CNTs and their derivatives are published. These materials are mostly used as coating formulations for different metals and alloys in various electrolytes. Modified carbon allotropes show remarkable solubility in the polar electrolytes therefore can be successfully used as aqueous phase corrosion inhibitors. Therefore, future research should be direct towards the designing and synthesis of soluble carbon allotropes derivatives. Their protection efficiency can be further enhanced using synergistic effect, that is, adding some inorganic salts like KI and ZnCl 2 .