Noble metal coating: The corrosion resistance of titanium rod is maintained by the oxide film formed on the surface. The formation reaction of such oxide film is generally expressed by the following formula: Ti+2H2O→TiO2+4H+ +4e This reaction is an anode reaction, so as long as the potential of titanium is increased, the reaction can be further carried out in the right direction, which means the stability of titanium oxide film and the improvement of corrosion resistance. But to improve the titanium potential, it is necessary to apply a high voltage from the opposite electrode, and at the same time, it is difficult to apply a uniform voltage in a large area, so it is not often used. In general, precious metals in harsh environment, also do not corrosion, high potential. Taking advantage of this, the surface of titanium coated with precious metals, titanium potential towards the side of the more expensive (high potential direction), thus improving its corrosion resistance. In precious metals, the cheaper Pd, Ru or their oxides (PdO, RuO2) are usually used for titanium coating. The corrosion resistance of titanium rods can be improved effectively by coating the metal or its oxides. The corrosion resistance of the coated materials is comparable to that of Ti/FONT>. 0.15Pd alloy is comparable. The disadvantage is that the precious metal film will peel from the titanium surface during prolonged use in fluids or fluids containing solids, although this peeling is rare. At present, Japan is developing coating methods with good density and properties, but the cost is higher. Gas method, because it must be heated at a temperature far higher than the titanium phase transition point, so that the structure, shape changes, resulting in products can not meet the requirements of use; However, CVD, PVD and PCVD methods require special equipment and large-scale equipment capable of mass production is under development with high cost. These treatments are rarely used to improve corrosion resistance and are sometimes used as a way to improve wear resistance. Pb+, Pt+ implantation (ion beam, electron beam) ion implantation surface modification is very effective to improve the corrosion resistance, but the cost is higher, is under research, not yet practical.