Current Overview of Corrosion Inhibition of API Steel in Different Environments.

API (American Petroleum Institute) steels are the most employed metal alloys in the oil industry due to their outstanding mechanical properties; however, their protection is considered as an imperative matter because of their corrosion damage vulnerability when exposed to different surroundings that provoke a rate increase in the concomitant redox reactions. This problematic situation becomes more relevant when the generation and/or use of one or various aqueous corrosive environments occur, in addition to process conditions, the result of which is extremely difficult to be controlled. For these reasons, the internal and external protection of exposed metallic systems are considered as a fundamental concern, where internal corrosion is often controlled through the addition of corrosion inhibitors (CIs). The present review analyzes researchers' contributions in the last years to the study and evaluation of CIs for API steel in different corrosive media featuring HCl, H 2 SO 4 , H 3 NSO 3 H, CO 2 , H 2 S, NaCl, and production water under different temperature and flow conditions. Different CIs derived from plant extracts, drugs, nanoparticles, or ionic liquids, mainly destined for acid media, were found. Throughout the review, an exhaustive analysis of inhibition process results is carried out based on gravimetric and/or electrochemical techniques that consider the weight loss of the metallic material and electrical behavior (current density, resistance, capacitance, frequency, impedance, etc.). Likewise, the results of computational analyses and those of surface analysis techniques were taken into account to reinforce the study of CIs.