Synthesis of Silica/Hydroxyapatite Nanocomposites Using Rice Husk and Fish Scale for Corrosion Protection Application

In this study, we report the synthesis of silica/hydroxyapatite (HAp) nanocomposites by employing rice husk-derived SiO 2 (RH-SiO 2 ) and fish scale-derived HAp (F-HAp) using planetary ball mills with 75 wt.% SiO 2 :25 wt.% HAp (SH-1) and 50wt.% SiO 2 :50 wt.% HAp (SH-2). SH-1 consists of spherical silica nanoparticles covered with irregularly shaped HAp nanoparticles, while SH-2 consists of aggregated spherical nanoparticles where the HAp and silica components are indistinguishable at the nanoscale. The potentiodynamic polarization curve revealed that the corrosion rate of RH-SiO 2 , F-HAp, SH-1, and SH-2 coated mild steel was 1.84, 0.56, 0.35, and 0.19 mm/yr, respectively. Nyquist and Bode's plots indicated that the composites provide more resistance to corrosion on mild steel than either F-HAp or RH-SiO 2 . Also, the SH-2 composite demonstrated greater corrosion protection than the SH-1 composite. The higher corrosion resistance of nanocomposites (SH-1 & SH-2) may be attributed to the barrier established by the simultaneous release of calcium, phosphate, and silicate ions on the surface of mild steel. This research suggests a method for preventing corrosion by employing low-cost biowaste products.