Use of chemical corrosion inhibitors is quite common in production and processing operations. Depending on the type of acids used, different inhibitors have been developed to minimize corrosion and enhance the life of metal tubulars. Development of new chemicals and chemistries, which maintain good protection of materials under a variety of conditions while being environmentally acceptable, is an extremely challenging task.

This paper investigates the inhibitive properties of a new environmentally acceptable inhibitor toward corrosion of different steel alloys in the presence of mineral and organic acids. The inhibitor explored in this paper is a food grade chemical derived from a plant and commonly used in medicinal formulations. It is easily available, non-polluting, and biodegradable, being of plant origin. The inhibitor composition has several N, O, and S atoms containing alkaloid structures, which helps enhance the adsorption capacity of the chemical as well as imparts corrosion inhibition properties. The inhibitor can be used either in the form of a solid powder derived from the roots of the plant or in a liquid form derived by means of extraction.

Corrosion inhibition of oilfield alloys, such as N-80, 13Cr-L80, and QT-800, were studied in the presence of corrosive media, such as 7.5 and 15% HCl acid, and organic acid mixtures comprising acetic and formic acid. Weight-loss measurements were used to evaluate the inhibition efficiency and a corrosion loss of ≤ 0.05lb/ft2 was considered as a pass. Tests were conducted on the metallurgies mentioned over a temperature range of 150 to 275°F.

The results disclosed illustrate the potential of the inhibitor to serve as an effective environmentally acceptable inhibitor for the corrosion of steel alloys in the described temperature range. This single inhibitor composition can be applied for both HCl and organic acid media in fresh water and salt brine systems.

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