Pengaruh tegangan dan konsentrasi elektrolit H3PO4 pada proses anodisasi terhadap lapisan warna, kekasaran permukaan dan biokompatibilitas material implan Ti-6Al-4V = Effect of voltage and H3PO4 electrolyte concentration during anodizing on the resulting coloured oxide film, surface roughness and biocompatibility of Ti-6Al-4V as an implant material