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ADVANCED MATERIALS AND COATINGS FOR CORROSION CONTROL

SIXTEENTH NATIONAL CONGRESS ON CORROSION CONTROL

Organised by NCCI, in association with CSIR-CECRI, IOCL & Berger Paints

23 August 2012

ADVANCED MATERIALS AND COATINGS FOR CORROSION CONTROL

By

Dr. A Sivathanu Pillai

Distinguished Scientist & CCR&D, DRDO & CEO & MD, BrahMos Aerospace

Mr. Vijaywargiya, Executive Director, IOCL Paradip, Dr. RK Malhotra, Director (R&D), IOCL Faridabad, Mr. Abhi

jit Roy, MD, Berger Paints Prof. Indranil Manna, Director CGCRI, Dr. Vijayamohanan Pillai, Director, CECRI, Distinguished men on the dais, Ladies and Gentlemen, My Greetings to all of you.

I am indeed honoured to participate in the 16th National Congress on Corrosion Control organised by NCCI in association with CSIR-CECRI, Indian Oil Corporation Limited and Berger Paints.

During the last 5000 years, unique cultures have come into existence as the man continuously attempted to have a better life for himself and the society around him. Even in the ancient times, people had a sound knowledge in the field of Metallurgy. The metallurgical works of ancient India namely the dancing girl of Mohenjodaro, the earliest known Indian lost-wax process cast bronze figure (dated as third millennium B.C.), the panchloka (five metals) idol of Lord Nataraja using investment casting process (dated as eighth century A.D.), the rustless 7 m iron pillar of Mauryan dynasty were evidence of a high degree of technical excellence in shaping metals and alloys as a single system. It is a testimony to the skill of ancient Indian metallurgists.

In the last 200 years, the society got transformed from purely agriculture to industrial, and then to information with different manifestations. The Industrial Revolution in the eighteenth century paved the way for development of new materials. Recent developments in bio and nanotechnologies and their convergence with information technology were opened up greater opportunities for the future. Emergence of smart and intelligent materials will revolutionise the human-machine interface through molecular nanotechnology.

The Corrosion pattern in India

A majority of the world’s population lives on the sea shores or near sea. India is no different. Many of the infrastructures both civilian and military and also strategic installations like nuclear reactors are all situated near sea. In the Indian sub-continent, corrosion is very severe near the shores and it goes on decreasing in severity as we proceed towards the Central India. Yet there also corrosion exists with moderate severity. In the North-West to North sector, the corrosion is very negligible.

India’s economy is hugely dependent on oceanic oil and gas installations, and also the oceanic armed forces to protect the land resources from sea borne aggressions. Hence, protecting these oceanic infrastructures and naval assets from corrosion, claims prime importance. Combat naval fleet, Patrol ships, Maritime Surveillance Aircraft, Arms and Ammunition dumps, Coastal Installations such as Surveillance Radars, Ship yards, Off-shore oil and gas rigs and many more are to be protected.

The consequences of corrosion are many and varied and the effects of these on the safe, reliable and efficient operation of equipment or structures are often more serious than the simple loss of a mass of metal. Failures of various kinds and the need for expensive replacements may occur even though the amount of metal destroyed is quite small. The overall cost involved in repair or replacement of the corroded components is huge. Approximately an amount of Rs. 1.5 lakh crore loss every year due to corrosion in various sectors, including infrastructure, utility services, production & manufacturing, and defence & nuclear waste. It is absolute necessary to control the corrosion losses. The situation may worsen due to the exponential growth of multiple sectors.

Naval materials in DRDO

To combat corrosion, DRDO has developed AB class of steel, non corrosive silicon steel, Anti corrosive paints for naval ships, Fe-tic metal matrix composite materials, Self stratified coatings, Sacrifical anodes for naval ships, Hull protection technologies. AB Class of Steel is used in aircraft carriers. High build chlorinated rubber-tar anti-corrosive paints used for painting underwater hull and boot top areas, wetted areas of platforms and pontoons located in Sea. Solvent free anti-corrosive paint is used to paint the Interior compartment of ships, storage tanks for petroleum products and in areas that are prone to spillage of acid. Stratifiable paint blend comprising of epoxy and silicone alkyd resin has been developed with reduced solvent shows very good inter-coat adhesion between the layers. With a quick drying time of 3 hours and an over coating interval of 4 hours, this paint allows rapid underwater painting and the ships need not to be brought back to a dry dock. Indium activated aluminium based sacrificial anodes used for the underwater steel structures. Optimized composition of these anodes increases the efficiency to the tune of 90%. Platinised titanium anode-based ICCP has been developed for prevention of hulls from underwater corrosion. The system consists of auto control unit, reference electrode, and anodes. The Ag-AgCl reference electrodes have been developed to meet the requirement of the Navy for the existing ICCP system onboard ships. Also, electroless antifouling device based on cuprious oxide and polyvinyl alcohol/resin/teflon binders has been developed. The system starts leaching of copper as soon as it comes in contact with sea water and prevents fouling. The iron-based TiC particulate metal matrix composite is synthesised by aluminothermic reduction of oxide. The product can be cast into required shapes without the requirement of any external heat source and can be used to make wear/corrosion-resistant coating.

Nanotechnology in Corrosion Prevention

The recent advances in nanotechnology has ushered the applications of technology in every field. Nanotechnology offers one possible solution for creating new revolutionary anti-corrosion coatings capable of adapting to environmental damage and conditions. Nanoscience research and development aims to discover new properties and behaviors of materials at the nanoscale (1 to 100 nanometers (nm); 1 nm = 10-9 m). Nanomaterials are important due to their unique properties. Nanostructured materials are known for their outstanding mechanical and physical properties due to their extremely fine grain size and high grain boundary volume fraction. Significant progress has been made in various aspects of synthesis of nano-scale materials from synthesis to manufacture of useful structures and coatings having greater wear and corrosion resistance.

There are many nanotechnology based corrosion control coatings. Polycrystalline nanocomposites consist of conductive polymers display novel properties. Nanoparticulate dispersions of organic metal polyanilines in various paints at low concentrations can cause tremendous effects in corrosion protection. Nanoconducting polymers such as polyaniline, polythiophene and polypyrrole enhance corrosion resistance. 3-Coat Epoxy System - the epoxy primer formulated with Zinc dust and Single Wall CNT (SWNT) for dual barrier coating and cathodic coating protection. Self-Assembled Nanophase (SNAP) coating is a method of forming functionalized silica nanoparticles in situ in an aqueous-based sol–gel process, crosslinking the nanoparticles to form a thin film for protection of alloys from corrosion. Self-healing coatings are made by incorporating microcapsules (60 - 150 microns in diameter) and nanocapsules (10-100 nanometers) that contain film-formers and lead dust suppression compounds into the paint primers. When coating is scratched, the microcapsules break and spill their film formers, which protect the underlying substrates from damage, and repair some of the coating damage.

Nanoparticles incorporated in coatings have shown a dramatic resistance to corrosion of the substrate due to their hydrophilic, anti-wear, anti-friction and self-cleaning properties. Nanocoatings create a lotus effect and properties, which keeps corrosion away. The nanotechnology-enhanced corrosion control coating will prevent and combat corrosion degradation by directly targeting the thermodynamic enablers to corrosion, namely the galvanic cell formed between the anode, cathode, and electrolyte. Specifically, it will detect and repair small coating damage, detect and signal maintainers of moisture intrusion, detect corrosion and release inhibitors to combat corrosion, replenish its corrosion inhibitors from the environment, and integrate needed repairs to the coating.

CONCLUSION

The revolutionary properties of nanomaterials provide evolutionary properties to coatings and Nanotechnology approaches have resulted in coatings with improved adhesion and barrier and corrosion resistance. Nano-engineered smart coatings would achieve results that cannot be attained in conventional way. The industries concerned should give due concentration by employing technological solutions. The impact of corrosion could be significantly reduced by good ‘corrosion-smart’ designs with appropriate selection of corrosion-resistant material, use of corrosion prevention and control methods and ensuring planned corrosion maintenance. This will ensure lower life cycle costs, longer service life with higher reliability and readiness.

I am sure the deliberations of this congress will definitely be useful to the participants in the prevention and control of corrosion.

With this, I inaugurate the Sixteenth National Congress on Corrosion Control and my best wishes to all the participants of the Congress.

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