Coatings protective overcoats

Spin coating utilizes centrifugal forces created by a spinning substrate to spread a liquid evenly over its surface. Current applications are in photoresist technology for the microelectronic industry and in the manufacture of protective overcoats and adhesives for the optical storage industry (compact discs and DVDs).5... 

These films can be used as a protective overcoat to increase the life of many other potentially useful coatings in different applications, for example, the soft Indium-Tin Oxide film used in photovoltaic applications, soft YBaCu Oj superconducting thin films, etc. provided the diamond like overcoat does not alter or influence the basic properties of the underlying soft coating. 

Overcoats are an integral part of thin-film disk structures. Their primary role is to provide wear protection. The most common overlayers, such as Rh, plasma-polymerized coatings, SiOz, and carbon, are all chemically stable if they were fully to cover the disk surface, they would provide good corrosion resistance. The thinness of the overcoats and the roughness of the surface preclude perfect coverage and open up the path for localized corrosion at the sites where the magnetic layer is exposed to the environment. 

A schematic figure of the sensor element is shown in Figure 3.1.3. The outer surface is exposed direcdy to the exhaust gas, whereby plasma jet coating layer (called overcoat layer) is arranged as a ceramic protection layer [3]. The layer has Pt electrode retention for the sensor element surface, Pt sublimation velocity reduction. Further, the layer prevents against the attack of poisoning... 

An electrochemical study of the protectiveness of carbon overcoats as thin as 5 nm has been reported [141], Polarization resistance of disk structures in 0.5 M sulfuric acid was measured. Disks coated with hydrogen-containing ion beam deposited carbon were found to have much lower corrosion rates than those coated with standard sputtered C of equivalent thickness. The composition of the sputtered carbons was varied by changing the sputtering gas. The corrosion rate depended on the type of carbon ion beam C-H < sputtered C-H, < sputtered C-N < sputtered C. The different corrosion rates may be a result of differences in both coverage and catalytic activity of the carbon layers. 

---