Fabrication of “wooden ear”-like filler and anti-corrosion of composite coating under high temperature environment

Abstract

A composite coating composed of high temperature resistant fillers, resin and curing agent was fabricated to protect carbon steel from corrosion in 3.5 wt% NaCl solution and high temperature environment. In this work, the modification filler K-ZrP was prepared through the intercalation of α‑zirconium phosphate (α-ZrP) and the modification of KH550, which avoids the accumulation of filler during the preparation of coating, that is, the filler is evenly distributed in the coating. At different temperature (room temperature, 90 °C and 140 °C), the EP/K4 coating referring to the epoxy coating containing 4 wt% K-ZrP filler shows good corrosion resistance performance, which is reflected in electrochemical impedance spectroscopy and salt spray experiment. In particular, after soaking in 3.5 wt% NaCl solution at 140 °C for 7 days, the EP/K4 coating remained intact, while the other two comparison samples (EP, EP/α4 coatings which refers to the epoxy coating containing 4 wt% α-ZrP) are completely destroyed, the reason is that the microstructure of modified α-ZrP has better compatibility with epoxy resin. The “wooden ear”-like structure and functional groups guaranteed that K-ZrP could distribute uniformly in the system, fill the defects, block the corrosion medium, and most importantly, keep the nonliquidity property of coating under high temperature by forming skeleton structure of nanoparticle stack. Under this condition, the anti-corrosion performance of composite coatings could be improved. The microstructure of the skeleton structure formed by composite coatings in high-temperature corrosive media is more difficult to damage than that of pure epoxy coating.