**1. Introduction**

Generally, corrosion is regarded as the loss of a metal by the influence of corrosive agents [1]. However, in a broad sense, corrosion is the devastative consequence of chemical reaction between a metal or metal alloy and its environment [2]. General corrosion or uniform corrosion is the most prevalent form of corrosion that takes place on an entirely exposed metal surface *via* the electrochemical reactions in atmospheric or aqueous media and continues uniformly to cause the greatest destruction of that metal [3]. Even though only metals come to mind when describing corrosion, non-metallic materials, such as plastics, concrete, ceramics, rubber, etc. are prone to corrosion as well when exposed to different corrosive environments [4].

The difference in the potential energies of the corroding metal and the corrosion product is the fundamental force that drives the corrosion reaction. A certain amount of energy is required to be provided to naturally occurring minerals and ores to extract metals from them. Therefore, it is natural that these metals tend to revert back to their original state from which they were obtained when they are exposed to their environments. It is noteworthy that each metal is different in terms of the amount of energy required and stored in it or that is released during its corrosion. The greater the amount of energy needed during metal extraction, the more thermodynamically unstable is the metal and the shorter is its temporary existence in metallic form. Hence, corrosion has also been defined as the reverse of extractive metallurgy [1, 5].The electrochemical dissolution of a metal is the most important mechanism involved in its corrosion and makes the basis of all uniform and localized corrosion types. However, there are some corrosion types, such as oxidation, fretting corrosion, molten salt corrosion, etc. that can be described without reference to electrochemistry [1]. The mechanism of corrosion attack in an atmospheric environment and in an aqueous environment will be always governed by some

aspect of electrochemistry. Electrons will be flowing from certain areas of a metal surface to other areas through an electrolyte that is capable of conducting ions. This stems from the incredible tendency of metals to react electrochemically with water, oxygen, and other substances in the aqueous environment. In an electrochemical corrosion process, the anode is that area of the metal surface that is corroding due to the loss of electrons while the cathode is the area that consumes the electrons generated by the corrosion reaction [6].

Almost all of us are familiar with corrosion happening to metal structures, boats, steel pilings, household utensils, etc. Unfortunately, many of us are not aware of corrosion that is deteriorating the properties of underground water, oil, and gas pipelines crisscrossing our land or water pipes in the home where corrosion occurs mostly from the inside. Successful enterprises put in considerable efforts in controlling corrosion at the design stage and in the operational phase to avoid major corrosion failures, such as unscheduled shutdowns, fatalities, personal injuries, and environmental contamination in a modern business environment. However, even the best design is unable to foresee all conditions that can allow corrosion intruding into the life of a system [5]. Steel reinforced bar (rebar) can corrode in concrete without being noticed at all and can cause damage to buildings, bridges, parking structures, the collapse of electrical towers, failure of a section of highway, etc., resulting in a huge amount of repairing cost and threatening public safety [7]. This is why regular maintenance of the metallic components that are susceptible to corrosion is of paramount importance.

### **2. Impact of corrosion**

Even though the main reasons for considering corrosion are economic and ecological, losses due to corrosion or costs of corrosion can be actually divided into three main categories as shown in **Figure 1** [8].

#### **2.1 Material and energy**

The impact of corrosion on the equipment and its surrounding deserves a huge attention when it comes to designing an industry. Corrosion is considered to be one of the most challenging issues for most of the industrialized countries. Corrosion of tanks, piping, metal components of machines, bridges, ships, etc. can incur a massive material and economic losses upon a nation. Additionally, the safety of operating equipment, such as boilers, pressure vessels, metallic containers for toxic chemicals, bridges, turbine blades and rotors, automotive steering mechanisms, and airplane components can be threatened by corrosion failure [8]. Furthermore, the

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costs can be assessed.

*Green Corrosion Inhibitors*

**2.2 Economic**

*DOI: http://dx.doi.org/10.5772/intechopen.81376*

by the world is used to replace rusted steel [10].

well as those related to users (indirect) [5, 12].

devastative impact of corrosion goes beyond the metals and extends to energy, water, and the manufacturing phase of the metal frames [9]. It has been reported that one ton of steel turns into rust every 90 seconds, and, on the contrary, the energy needed to manufacture one ton of steel is approximately equal to the energy an average family consumes over 3 months. Approximately 50% of every ton of steel produced

Economic losses are classified into two types: (i) direct losses and (ii) indirect losses. Replacing the corroded structures and machinery of their components, for instance, mufflers, condenser tubes, pipelines, metal roofing, including necessary labor, repainting structures to prevent rusting, maintenance cost of cathodic protection system for underground pipelines, replacement cost of millions of domestic hot-water tanks and automobile mufflers, extra cost of using corrosion-resistant metals and alloys, galvanizing or nickel plating of steel, addition of corrosion inhibitors to water, and dehumidifying cost of the metal equipment storage rooms contribute to the direct losses. While it is quite difficult to assess the indirect losses, they have still been reported to add several billion dollars to the direct losses. Indirect losses include sudden shutdown of plants, loss of water, gas, or oil through a corroded pipeline, loss of efficiency in the energy conversion systems imposed by corrosion processes, contamination of water and food products in metal piping and containers, and overdesign requiring equipment to be designed many times heavier than normal operating pressure or applied stress to extend their lifetime [8]. Uhlig made the first ever systematic study on the cost of corrosion in 1949 [11]. Uhlig's report estimated the annual cost of corrosion in the United States to be US\$ 5.5 billion or 2.1% of the 1949 gross national product (GNP). This study measured the total costs by summing the costs related to anti-corrosion materials and corrosioninduced maintenance and replacement handled by owners and operators (direct) as

Corrosion cost studies using different methods, such as Uhlig method invented by Uhlig in 1949 [11], Hoar method invented by Hoar in 1971 [13], and economic input/output model devised by National Bureau of Standards (NBS) collaborating with Battelle Memorial Institute in 1978 [14] have been undertaken by several major economies, including Australia, China, Finland, Germany, India, Japan, Kuwait, the United Kingdom, and the United States [15]. A common observation of these studies was that the costs of corrosion ranged from approximately 1–5% of the GNP of each nation. The variation in the corrosion cost with respect to GNP was ascribed to the methodology used by each study and the specifics of each country [12].

A study done by National Association of Corrosion Engineers (NACE) as part of its International Measures of Prevention, Application, and Economics of Corrosion Technologies Study (IMPACT) revealed that the global cost of corrosion in 2013 was estimated to be US\$ 2.5 trillion which was equivalent to 3.4% of the global GDP in that year [15]. This study utilized the World Bank economic sector and GDP data to relate the cost of corrosion studies to a global cost of corrosion. In order to address the economic sectors across the world, the global economy was divided into economic regions with similar economies (according to World Bank). These were: United States, European Region, India, Arab World (defined by the World Bank), Russia, China, Japan, Four Asian Tigers plus Macau, and Rest of the World. However, the costs estimated typically do not include environmental consequences or individual safety. It is noteworthy that receiving additional funds for corrosion studies, or updated information on these studies, more detailed and accurate global

**Figure 1.** *Breakdown of corrosion costs.*

#### *Green Corrosion Inhibitors DOI: http://dx.doi.org/10.5772/intechopen.81376*

devastative impact of corrosion goes beyond the metals and extends to energy, water, and the manufacturing phase of the metal frames [9]. It has been reported that one ton of steel turns into rust every 90 seconds, and, on the contrary, the energy needed to manufacture one ton of steel is approximately equal to the energy an average family consumes over 3 months. Approximately 50% of every ton of steel produced by the world is used to replace rusted steel [10].
