Octadecylamine (ODA) is a well-known organic inhibitor for the corrosion protection of carbon steels. In the present study, electrochemical impedance data analysis was performed to extract physical parameters of the ODA thin film that formed on a P275 carbon steel surface. First, surface observations and contact angle measurements showed the steel surface modification after the ODA treatment linked to the adsorption of an organic hydrophobic thin film. X-ray photoelectron spectroscopy confirmed the presence of a very thin organic layer and revealed the presence of iron oxide/hydroxide underlying the ODA film. The impedance data analysis with a power-law distribution of resistivity in the organic film allowed the permittivity and thickness to be extracted. Finally, from the impedance results with and without ODA, the instantaneous corrosion inhibition efficiency was determined.

Crosslinked linear polyethylene/branched polyethylene blends have been studied by thermooxidation at different temperatures (between 60°C and 110°C), which are either below or above the melting temperature of each polyethylene in the blend.The modifications of the chemical structure of both polyethylenes and the blends were monitored by infrared spectroscopy during thermo-oxidation. The same oxidation products could be identified between the linear polyethylene and the branched polyethylene. Chemical derivatization treatments allowed confirming the thermo-oxidation mechanism of polyethylene and the same oxidation products for both polyethylenes. By using an Arrhenius approach, it has been shown that accelerated ageing above 80°C is not representative of thermal ageing below this temperature. Moreover, it was shown that there was no influence of the physical state of the polymer during thermal ageing on the observed non-Arrhenius behavior. Thus, extrapolating accelerated ageing tests to lower temperatures by an Arrhenius approach in order to predict the lifetime of the polymer leads to critical errors.

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.

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