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The purpose of this paper is to study the corrosion inhibition of carbon steel (CS) using a “green” inhibitor, polyvinyl pyrrolidone (PVP), in an aerated, alkaline medium containing 0.1M NaCl (blank) at pH 9 and pH 10. The effects of some additives, such as KI and untreated Saudi clay (UC) were investigated.

Weight loss method, surface studies, electrochemical impedance spectroscopy (EIS) and potentiodynamic polarisation were applied.

The inhibition efficiencies of blank solutions with 1000 ppm PVP ranged from 66‐78% for weight loss results and from 23‐66% for the electrochemical tests. The EIS results indicated that the adsorption of PVP led to the formation of a protective film on the metal/solution interface. Tafel results indicated that PVP is a mixed‐type inhibitor. The addition of KI to PVP and the blank solution significantly increased inhibition efficiency, while the addition of UC reduced the inhibition efficiency. Adding KI resulted in a high surface‐area coverage ranging from about 91% after one hour to about 81% after 45 hours. The adsorption mechanism was fitted with a Langmuir isotherm.

This is a static study, whereas in oil drilling there is a dynamic system; however the findings may apply to both systems.

Carbon steel is used in alkaline and neutral media in the petroleum industry. The effect of KI additives was examined.

The paper shows how it may be possible to reduce the cost of repair of equipment and lower the environmental impact of corrosion.

There are few studies which investigate the combining effect of polymer and KI in alkaline medium containing NaCl.