Achyranthes aspera (AA) extracts were studied as corrosion inhibitor for mild steel (MS) in industrial water medium using mass loss and electrochemical techniques. The results of the study revealed that AA extracts inhibit MS corrosion through adsorption process following Langmuir adsorption isotherm model. The protection efficiency increased with increase in inhibitor concentration and decreased with temperature. The electrochemical impedance spectroscopy (EIS) measurements showed that the charge transfer resistance increases with increase in the concentration of AA extracts. The polarization curves obtained indicate that AA extracts act as mixed type of inhibitor. Scanning electron microscopy (SEM) was used to analyze the surface adsorbed film. 1. Introduction The use of inhibitors is one of the most practical methods for protection against corrosion and prevention of unexpected metal dissolution. Different organic and inorganic compounds have been studied as inhibitors to protect metals from corrosive attack. The efficiency of these organic corrosion inhibitors is related to the presence of polar functional groups with S, O, and N atoms in the molecule [1–5]. Such compounds can adsorb onto the metal surface and block the active surface sites, thus reducing the corrosion rate. Nevertheless, most of these compounds are not only expensive but also toxic for living beings. So, plant extracts have attracted the attention of researchers as ecofriendly corrosion inhibitors for many decades [6–9]. Plant extracts are an incredibly rich source of natural chemical compounds that can be extracted by simple procedures with low cost and are biodegradable in nature. The actual inhibitors in the plant extracts are usually alkaloids and other organic nitrogen bases, as well as carbohydrates, proteins, and their acid hydrolysis products [10]. Alkaloids have an ability to coordinate the transition metals or their alloys via the d-orbitals of metal and empty p-orbitals of the heteroatoms in the inhibitor molecules. A number of natural compounds have been used as corrosion inhibitors for metals and their alloys in acidic, alkaline, and neutral solutions [11–15]. Achyranthes aspera (AA) is one of the most important antioxidant medicinal plants, and it is an excellent source of several flavonoids, tannins, reducing sugars, alkaloids, and saponins [16]. Besides these phytoconstituents, several glycosides [17], fatty acids [18], ecdysterone [19], and triterpenoids [20] were isolated in various parts of plant. In the light of phytoconstituents reported, the present study was
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