Film-Forming Amines for the Corrosion Protection of Carbon Steels in Nuclear Power Plant Secondary Circuit Conditions: An Impedance Study

Abstract

Octadecylamine (ODA) has been the subject of numerous investigations for the corrosion protection of carbon steels in nuclear pressurized water reactors (PWR). In the present work, electrochemical impedance spectroscopy was used to study and to compare the ODA behavior after different treatment temperatures (from 80 °C to 275 °C) representative of the secondary circuit of the PWR. The ODA films were characterized at room temperature. The impedance data analysis allowed the ODA film parameters (thickness and permittivity) to be obtained. The ODA film thickness was independent of the treatment conditions and was about 20 nm. At 120 °C and 220 °C, the presence of magnetite, formed during the treatment in the autoclave, strongly improved the corrosion protection afforded by the ODA films. An instantaneous inhibitive efficiency of 99.9% was assessed. At 275 °C, thermal degradation of the ODA molecules was shown.