Environment Friendly Corrosion Inhibitors for Alloys or Metals

Environment Friendly Corrosion Inhibitors for Alloys or Metals

Naturally Occurring Wastes and Plants

Corrosion is defined as the deterioration and consequent loss of metals or alloys by chemical or electrochemical reaction with the environment. Corrosion reduces the service life of the equipment causing heavy economic losses. There are certain chemicals which act as corrosion inhibitors that react with the surface of metal exposed to the environment and giving a certain level of protection. Corrosion inhibitors protect the metal by adsorbing themselves on the metallic surface by forming a layer between the metal and environment.

Corrosion inhibitors are organic and inorganic compounds containing N, S, and O atom act as corrosion inhibitor through co-ordinate bonding but they are toxic to environment and human being and expensive as well.  Nowadays, Emphases have been given to the development of eco-friendly corrosion inhibitors. Natural products are incredibly rich sources of naturally synthesized chemicals used in most of the applications.  Some  of  the  advantages  that  natural  products  have  over  other  types  of  chemicals  include  being  environmentally  acceptable  and  is  a  readily  available  resource. They are the richest sources of ingredients which have very high corrosion inhibition efficiency. Most of the naturally occurring substances from plants are safe and can be extracted by the simple and cheap procedures. Development and identification of such environmentally benign corrosion inhibitors is the prime demand of the time.

Scientific Utility

The industrial expansion is a part of overall development of the country which leads to the development of new products and processes, specialized equipments and new materials of construction. Materials science, engineering and technology has emerged as an independent discipline during the last decade. These developmental changes have brought up the significance of corrosion problems and the immediate urgency to apply preventive methods. A corrosion inhibitor is a chemical compound (synthetic and natural) that, when added to a liquid or gas, decreases the corrosion rates of materials particularly metals and alloys. 

Any developing country like India had to face the challenge posed by corrosion, and there is now an increasing awareness of the imperative need for corrosion inhibition  research and the applications of the findings to meet specific situations. The corrosion costs in most of the countries are in the range of 2-4 percent of the gross national product. So it is important that economically and ecofriendly useful measures should be taken to minimize corrosion. Relatively higher growth rate corrosion inhibitor markets are expected in the developing regions because of increasing industrial production.

Increased service life of the costly equipments can be achieved by proper maintenance and routine cleaning of the equipment for the removal of scale and deposits are essential. The removal, of surface deposits, is important for reducing the corrosion of the equipment and to maintain the heat transfer of the equipment. Inorganic acids, organic acids and certain solvents are typically employed for this purpose. Mineral acids have proved very effective in the efficient removal of scales and deposits on industrial equipment. Hydrochloric acid (HCl) has been shown to be used particularly efficient in the removal of scales. Since, most metals are soluble in mineral acids therefore metal degradation is obvious which is also responsible for equipment failure.

World consumption of corrosion inhibitors is expected to grow at an average annual rate of 2.4% during 2008–2013. National Research Development Council (NRDC), India reports that CSIR laboratories are developing many types of corrosion inhibitors for various industrial applications. Organic compounds containing N, S, or O hetero atoms that act as corrosion inhibitor by adsorption on metal surface though co-ordinate bonding. Such inhibitors are usually toxic to the environment and human being as well. Plant extracts have been found more useful, naturally occurring, low cost, biodegradable, environment friendly and renewable corrosion inhibitors instead of using organic compounds.

Author: Dr. Renu Singh, Department of Chemistry, Maharishi University of Information Technology, Lucknow

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