Effects of technical Kraft lignin-based epoxy coatings under high pressure and high temperature

Epoxy-based anticorrosive coatings are often applied on steel structures to provide protection against corrosion in extreme environmental conditions, and are widely used in the oil and gas industry. To minimize the reliance on fossil fuels in anticorrosive coatings, there is a rising demand to integrate renewable raw materials into coating formulations.

In this study, a non-stirred batch reactor was used to simulate the high pressure and high temperature (HPHT) conditions, where lignin-based epoxy novolac (L-EN) coatings were exposed to different corrosive environments, consisting of a gas phase (a mixture of N2 and CO2), a hydrocarbon phase (para-xylene) and a seawater phase (3.5 wt% NaCl solution). The stability of L-EN coatings at HPHT was evaluated and compared with a commercial epoxy novolac coating and a neat (i.e., pigment free) coating. Compared to neat EN, the L-EN coatings did not show any surface defects up to 120°C and 100 bar under seawater and gas conditions. Subsequently, to identify the chemical changes in (L-EN) coatings after the HPHT test, an FTIR measurement was conducted and compared with the neat EN coating. No significant changes other than the hydroxyl, epoxy and carbonyl peaks were observed after the HPHT exposure. Other characterization techniques such as microscopic analysis, differential scanning calorimetry (DSC) and adhesion tests were performed.