Eco-friendly Corrosion Inhibitors<br />By<br />Asst. Lect. Zahraa Abdulelah Hadi<br />Corrosion is the destructive attack of a metal by chemical or electrochemical reaction with its environment. Corrosion occurs at different appearances according to corrosive environment, metal, corrosion products’ nature, and other factors including stresses on the metal, relative velocity of the environment and metal, and temperature <br />Many methods have been developed to prevent corrosion and to improve the service life like cathodic protection, the reinforcement coating, electrochemical approaches and inhibitors of corrosion.<br />U.S. Environmental Protection energy (EPA) classifies corrosion inhibitors that contain vanadium, antimony, copper and thiocyanate <br />compounds as toxic pollutants. Due to this toxicity, the present works focus on the usage of eco-friendly corrosion inhibitors which are available, inexpensive and renewable.<br />Adding of inhibitors, which are substances that can prevent or reduce corrosion, is regarded as one of the main approaches to minimize corrosion rate in metals. <br />Many factors affect corrosion in reinforcing concrete include oxygen, moisture availability, relative humidity, temperature, carbon dioxide, chloride ions, acidic gaseous pollutants, cover over reinforcing steel, cement composition, impurities in aggregate, mixing and curing water, and concrete permeability. <br />Corrosion inhibitors, thus chemical compounds added as admixtures to the fresh concrete to improve the durability of concrete structures. The use of corrosion inhibitors is of increasing interest as they are claimed to be useful in reinforced concrete not only as preventative measure for new structures (as addition to the mixing water) but also as surface-applied inhibitors for preventative and restorative purpose.<br />Due to the toxicity of chemical inhibitors and their hazards to the environment, the researchers guided their goal to find eco-friendly, inexpensive, biodegradable, and non-toxic corrosion inhibitors. Some of these inhibitors are listed below: <br />1.Green Inhibitors <br />Plant extract materials were a choice to be eco-friendly corrosion inhibitors, they contain heteroatoms such as P, N, S, and O. The protective films are formed due to the coordination of these atoms with corrode metal atoms. These inhibitors were used to protect different type of metals in different mediums. Also, plant extract inhibitors can be used either alone or in combination with other inhibitors. <br />Researchers used different parts of the plants to extract as green corrosion inhibitors such as leaves, fruits, flowers, seeds, and barks. The extract operation can be done by different type of solutions such as alcohol, acid, and water. <br />2. Drugs Inhibitors <br />Over the past two decades, extensive and development have led to the discovery of new classes of corrosion inhibitors, and the importance on the use of several drugs as corrosion inhibitors has grown. Recently, the use of antibiotics and other drugs have been investigated and their inhibition efficiencies have been linked with their heterocyclic nature. <br />Most of heterocyclic drugs are environmentally friendly and can favorably complete with the natural products. In recent years, the use of pharmaceutical compounds offer interesting possibilities for corrosion inhibition due to the presence of hetero atoms like nitrogen, sulphur, oxygen and π- bond in their structure and are of particular interest because of their safe use, high solubility in water and high molecular size. <br />