# Recent Trends and Progress in Corrosion Inhibitors and Electrochemical Evaluation
## 1 Introduction  
Corrosion has become a worldwide phenomenon that affects many areas, such as industries (oil and gas). Corrosion is caused by corrosive species commonly found in the air, leading to the deterioration of metal through electrochemical and chemical processes. This degradation occurs when the metal is exposed to atmospheric moisture, and it is dependent on both time and temperature [1]. It damages the beauty and glaziness of the metal materials; for example, cracks have appeared in certain areas of the Taj Mahal, India, etc. The steel inside the building is corroded and causing fractures because most metals rapidly undergo corrosive degradation through the reactivity of components in the surrounding environment because they are thermodynamically unstable in their pure form [2; 3; 4]. Different countries have conducted surveys on national cost corrosion. According to this survey, the economy of the US was reduced by $70 billion, which is 4.2% of the gross national product, due to corrosion. The government of India spends approximately 3.5% of the country GDP per year on corrosion losses [5]. Due to the abovementioned factors, it is important to prevent corrosion. When metallic sections corrode quickly and must be replaced, it becomes a high-cost process. Furthermore, the procedure of addressingcorrosion is risky and dangerous, posing the potential to harm personnel or even lead to fatalities. This issue impacts health, safety, economy, technology, and culture. Corrosion in industries is mainly due to acid-based cleaning and rust removal on various equipment, like metal pipes, wheels, and various machineries [6]. In the field of corrosion prevention, it has been shown that inhibitors have been the subject of the most research. Corrosive damage to metallic materials is prevented through inhibition, involving the use of chemical compounds. These compounds, known as corrosion inhibitors (CIs), reduce corrosion rates and impede the diffusion of corrosive ions in a corrosive environment caused by chemical elements within the corrosion system [7]. While increased corrosion protection is needed, the major driving force is that CIs that previously worked extremely well can now no longer be used due to their risks to health. Chromium-based corrosion inhibitors, such as hexavalent chromates (CrVI), were widely used for their effectiveness in preventing corrosion. However, these inhibitors have been found to be toxic and carcinogenic, posing serious health and environmental risks, and currently no alternatives have been identified that are both safe and effective in reducing corrosion. Depending on the morphology of metal damage, corrosion is categorized into general corrosion, pitting corrosion, crevice corrosion, intergranular corrosion, environmentally induced fracture, de-alloying, galvanic corrosion, erosion, and corrosion based on the metal damage's morphology [8]. Atmospheric corrosion is one of the most common forms of corrosion. Infrastructure, transportation, energy, and other industries are all significantly impacted by atmospheric corrosion, which is influenced by a variety of environmental conditions. An important environmental factor is relative humidity. Rainfall can have an impact on how metallic materials react to air corrosion [9; 10; 11]. When steel is exposed to corrosive environments, it begins to deteriorate over time due to fatigue. Seawater environments speed up the development and progression of crack growth. In offshore structures, this has been discovered to be a significant failure mechanism [12]. There are a few ways to prevent corrosion on metal, as shown in Figure 1, including coating [13], alloying [14], cathodic protection [15], anodic protection [16], organic coatings [17], and, more recently, researchers are using a laser technology [18] for surface treatment of metal is to improve the properties of metals, such as their roughness, hardness, and corrosion resistance.