# Review on Corrosion Inhibitors for Oil and Gas Corrosion Issues
## 3 Commercial Corrosion Inhibitors  
As problems related to the corrosion issue have been skyrocketing, especially in the oil and gas industries, corrosion scientists have developed various techniques to mitigate this issue, such as corrosion inhibitors [35], cathodic protection [36], and paint-based corrosion inhibitors [37]. Most of the corrosion inhibitors utilized are mainly organic and inorganic composites, where organic inhibitors reduce corrosion through adsorption techniques, while the inorganic ones prevent corrosion by reacting with the anodic or cathodic parts of the process [38; 39].  
Organic compounds that consist of nitrogen, oxygen, and/or sulfur are considered as competent industrial corrosion inhibitors [40]. These inhibitors inherit the ability to form a protective layer between the metal surface and corrosive environment [41] through the adsorption process to delay the metal disintegration [42; 43; 44]. For instance, azide and pyrimidine byproducts are the most-used inhibitors to minimize the corrosion of metals and alloys by injecting the inhibitors into the system at low treatment concentrations [45; 46]. In addition, organic inhibitors have the tendency to work productively in all acid concentrations and do not poison the refinery catalysts.  
Nevertheless, the disposal of contaminated industrial corrosion inhibitors results in damaging effects on the ecosystem; thus, the use of green and environmental-friendly inhibitors is on the rise [47; 48]. To illustrate, the benzotriazoles that are usually utilized to minimize the corrosion of heat exchangers were proven to poison marine creatures, even at concentrations as low as 3 ppm [49]. However, organic inhibitors chemically reduce as time passes in the presence of acid yet cannot withstand at temperatures above 95 \({}^{\circ}\)C; furthermore, their use is expensive.  
Next, inorganic corrosion inhibitors contain the salts of zinc, copper, nickel, arsenic, and additional metals, with the arsenic compounds being the ones that are most commonly used. When these arsenic compounds are mixed with the corrosive solution, they scrap at the cathode cell of the unprotected metal surfaces. The plating reduces the percentage of hydrogen ion interchange due to the formation of iron sulfide amid the steel and acids that act as an obstacle. The reaction of acid with iron sulfide is known as a dynamic process. There are advantages as well as disadvantages when using the inorganic inhibitors. The advantages are they work excellently at high temperatures for longer periods and are less expensive than organic inhibitors. As for the shortcomings, inorganic inhibitors are more likely to lose their grip in acid solutions that are stronger than 17% hydrochloric acid, tougher to combine, and might release toxic serine gas as the product of corrosion.  
Although these inhibitors are potent at high concentrations, they are unarguably damaging to the environment. In conjunction with this problem, new inhibitors concentrating on polymers [50; 51; 52] and plant-based [53; 54] substances were studied. However, polymers were defined as moderate inhibitors, needing secondary refinement that will only result in higher cost [55; 56]. Thus, extensive research is being undertaken on plant parts, as they are easily accessible in an inexpensive way.