Titanium polishing

1, What is titanium polishing
Titanium polishing is the process of producing a high gloss or lustrous finish on a titanium surface. The process can be applied to different types of titanium, including commercial grade, medical grade or aerospace grade. Polishing y enhances the durability, corrosion resistance and aesthetics of titanium parts such as jewelry, watches, medical implants or aircraft.

2, different types of titanium polishing
(1) Mechanical polishing method
　　The use of different specifications of soft cloth wheel or black brush, dipped in titanium and titanium-containing alloy special polishing paste to titanium and titanium alloy surface polishing method. In the polishing of titanium castings, must do completely clear casting surface pollution layer and not occurring new grinding hardening layer, will not be able to achieve the desired polishing effect. Polishing is still using high speed and light pressure. The use of green polishing paste, which the authors tested for use in polishing castings made of titanium and titanium alloy, produced results that were more appealing. Polished titanium and titanium alloy castings can not be immediately into the wash, must be completely formed after the surface oxide film before washing, otherwise the surface will produce darkening phenomenon.
(2) chemical polishing: chemical polishing is through the oxidation reduction reaction of metal in the chemical medium to achieve the purpose of leveling polishing. The advantage is that chemical polishing and metal hardness, polishing area and structure shape, where the parts in contact with the polishing solution are polished, without special complex equipment, easy to operate, more suitable for complex structure of titanium denture bracket polishing. However, the process parameters of chemical polishing is difficult to control, requiring a good polishing effect on the denture without affecting the precision of the denture. The best chemical polishing solution for titanium is HF and HNO3 in a specific ratio. HF is a reducing agent that can dissolve titanium metal and play a leveling role; Its concentration should be lower than 10%. HNO3 plays an oxidizing role that stops hydrogen absorption and titanium dissolution while also producing a bright effect. Titanium polishing solution requires high concentration, low temperature, short polishing time (1~2min.).
(3) electrolytic polishing: also known as electrochemical polishing or anode dissolution polishing, due to the low electrical conductivity of titanium, oxidation performance is very strong, using water acidic electrolyte such as HF-H3PO4, HF-H2SO system electrolyte for titanium almost can not polish, apply external voltage, titanium anode immediately oxidation, and make the anode dissolution can not proceed. But the use of anhydrous chloride electrolyte at low voltage, titanium has a good polishing effect, small test pieces can get mirror polishing, but for complex restoration body still can not achieve the purpose of complete polishing, perhaps the use of changing the shape of the cathode and additional cathode method can solve this problem, there is still a need for further research.

3, the benefits of polished titanium parts
(1) high surface finish, with better visual effects.
(2) Increased surface hardness and better wear resistance.
(3) Good surface cleanliness, not easy to contaminate, better corrosion resistance.
(4) Reduce the surface roughness and improve the precision of the parts.
(5) Improve the surface flatness, can better match other parts.
(6) Increase fatigue resistance and durability, and improve the service life of the parts.

4, polished titanium parts applications
Various fields such as aviation, aerospace, metallurgy, chemical, electronics, electric power, medical, sports equipment, etc.

5, other titanium surface treatment options
(1) anodic oxidation: titanium anodic oxidation technology is relatively easy, in some oxidizing medium, under the action of the applied voltage, titanium anode can form a thicker oxide film, thereby improving its corrosion resistance and wear resistance and weather resistance, anodic oxidation electrolyte is generally used H2SO4, H3PO4 and organic acid aqueous solution.
(2) Surface roughening: In order to improve the bonding performance of titanium and finishing resin, the surface of titanium must be roughened to improve its bonding area. Clinical use of sandblasting roughening treatment, but sandblasting will cause titanium surface aluminum oxide pollution, we use oxalic acid etching method, to get good roughening effect, etching 1h surface roughness (Ra) can reach 1.5 ± 0.3μm, etching 2h
Ra is 2.99±0.57μm, which is more than double the Ra of sandblasting alone (1.42±0.14μm), and its bond strength is increased by 30%.
(3) surface treatment against high-temperature oxidation: In order to prevent titanium oxidation in several sentences at high temperatures, the formation of titanium-silicon compounds and titanium-aluminum compounds on the surface of titanium can prevent the oxidation of titanium at temperatures above 700°C. This surface treatment of titanium oxidation at high temperatures is very effective, perhaps the titanium surface coated with such compounds, titanium porcelain bonding is beneficial, still need further research.