TABLE 2.

Main results of chemical methods application on titanium and its alloys.

Methods	Coating quality	Process rate	Bond strength	Osteogenesis and antibacterial function	Applications
Chemical vapor deposition (Du et al., 2016; Youn et al., 2019)	Good controlling on composition and characteristics of the film, flexibility	Deposition by chemical reaction at a high temperature	Not available	It positively affects the proliferation and activity of osteoblast-like cells, sterilization efficiency against E. coli	Used for complex workpieces and inner hole coating
Sol-gel (El hadad et al., 2020; Ziabka et al., 2020)	Easy to prepare uniform multi-component oxide film and quantitative doping, effective control on composition and microstructure	Several steps for the preparation of sol-gel, transfer of sol-gel to substrate, aging and drying	3–55 MPa	Bone-like apatite formation in SBF, good biological activity. antifungal effects	Used for preparing thin films, possible for coating on the surface of particles of powder materials
Micro-Arc oxidation (Sedelnikova et al., 2017; Li et al., 2018)	Suitable for ceramic membrane, firm bonding, dense and uniform ceramic membrane	≈1–3 μm min–1 in thickness	5–44 MPa	Improving the adhesion of cells. Good antibacterial ability against E. coli and Staphylococcus aureus	Used for improving the surface roughness