Effects of multiwall carbon nanotube addition on the corrosion resistance and underwater acoustic absorption properties of polyurethane coatings

In this study, the effect of multiwall carbon nanotube (CNT) addition on the anticorrosion and underwater acoustic absorption properties of polyurethane (PU) coatings was studied. The corrosion and mechanical properties of various coatings were characterized through electrochemical impedance spectroscopy, polarization curve measurement, salt spray tests, pull-off tests, and dynamic mechanical analysis. Underwater acoustic absorption properties were evaluated using an underwater acoustic impedance tube system comprising two hydrophones, a sound and vibration data acquisition module, a power amplifier, and a speaker. The results indicated that the corrosion resistance and adhesion strength of the PU coating was enhanced by adding 0.4 wt% CNTs. When additional CNTs were added (1 wt%), however, the corrosion rate of the coating increased. Measurement of the underwater sound absorption coefficient revealed that the underwater acoustic absorption properties of the PU + CNT composite coatings increased as the CNT content increased to 1 wt%.