**3. Non-toxic corrosion inhibitors**

The toxicity of inhibitors and the increase in environmental pollution have led to the enactment of strict international laws for the use of ecological inhibitors and to the demand for a green and ecological approach that deals with the principles of "green chemistry". These principles refer to efforts toward establishing a comprehensive approach to chemical risk management. This concept is based on the ideas of sustainability, reducing environmental consequences, and preserving natural resources for the following centuries [16]. The requirements for a chemical to be approved as a green corrosion inhibitor have been explicitly set out by legislative bodies essentially the Paris Commission (PARCOM) and the Registration, Evaluation, Authorization, and Restriction of Chemicals (REACH), which are non-bio-accumulative, biodegradable, and zero or very minimal marine toxicity level [17]. **Figure 1** illustrates the principles by which green corrosion inhibitors work.

#### **Figure 1.**

*The principles of green chemistry on which green corrosion inhibitors act.*

The major categories of these kinds of inhibitors include plant extracts, oils, rare earths, and amino acids have been discussed briefly below. Other green inhibitors such as ionic liquids, organic polymers, and surfactants [18–20] are not emphasized in this chapter.

Green corrosion inhibitors are drawing extraordinary interest in the corrosion field and can be used in many industrial applications [11] to promote green chemistry and sustainability. In this perspective, one of the areas in which green chemistry is associated with green inhibitors, through the reduction of ecological impact and wastes, is related to safeguarding metals. **Figure 2** shows the importance of green corrosion inhibitors in large industrial applications.
