Study of Aminophosphonic Acid Molecules as Corrosion Inhibitors

Abstract Some common corrosion and scale inhibitors possess similar molecular features, such as Lewis bases functional groups, which allow them to adsorb onto metal surfaces, minimizing scale and/or corrosion processes. Even though both types of inhibitors are indispensable for correct oil & gas operations, there is a technological gap about how one can act as the other, especially in an aggressive medium as produced water. Thus, the present work evaluated the corrosion protection given by two commercially employed scale inhibitors (i) Diethylene Triamine-Pentamethylene Phosphonic Acid (DTPMP) and (ii) Polyamino Polyether Methylene Phosphonic Acid (PAPEMP) on AISI 1020 in synthetic produced water. Their corrosion protection efficiencies were assessed by post-immersion morphological analysis, electrochemical analysis in static flows, such as open circuit monitoring, electrochemical impedance spectroscopy (EIS) and linear polarization resistance, and weigh loss test in a dynamic loop test. Results showed that PAPEMP, under improved conditions, yielded better protection with a corrosion rate of 0.0062 mm/year after 7 days in the loop experiment. Nevertheless, despite the evident corrosion protection shown within the results, the aminophosphonic acid scale inhibitors presented low calculated corrosion protection efficiencies in synthetic produced water due to the formation of deposits on the blank sample.