COMMERCIAL POLYURETHANE CLEAR COAT REINFORCED WITH CARBON NANOTUBES AND HYDROXYAPATITE POWDERS

Advanced anticorrosive coatings are used in practical applications across various industries, including electronics, biomaterials, automotive and aerospace sectors. Among ceramics, hydroxyapatite (HA) stands out due to its high corrosion resistance and chemical stability. In this study, HA powders were synthesized via the hydrothermal method using calcium nitrate (Ca(NO3)2•4H2O) and di-ammonium hydrogen phosphate ((NH4)2HPO4), with the addition of surfactants to modulate their morphology. X-ray diffraction analysis confirmed the hexagonal phase of HA with a crystallite size of approximately 20 nm. Scanning electron microscopy (SEM) revealed a nanorod morphology with varying lengths. The HA powders were then blended with multi-walled carbon nanotubes (MWCNTs) poured into a commercial polyurethane clear coat to develop an advanced anticorrosive coating. This composite coating, containing varying loadings of MWCNTs and HA powders, was applied to commercial low-carbon steel (ASTM A1008). Image segmentation analysis quantified the oxide percentage on the coated surfaces. Notably, HA nanorods synthesized using cetyltrimethylammonium bromide (CTAB) as a surfactant and combined with MWCNTs at concentrations of 20 mg HA and 1 mg MWCNTs effectively reduced the oxidation percentage from 28.76% to 4.01%.