Chromium coatings deposits

FIGURE 24.2 Relationships of the level of damages (a) and vacancy to nitrogen atom ratio (b) as a function of thickness of a chromium coating (deposition time) deposited under the bombardment with nitrogen ions... 

Under micro-discontinuous chromium coatings, copper undercoats improve corrosion resistance. On non-conductors, especially on plastic substrates, copper is often applied before nickel-chromium plating over the initial electroless copper or nickel deposit in order to improve ductility and adhesion, e.g. as tested by the standard thermal-cycling test methods ... 

A thickness of at least 0-8 xm is normally needed to ensure that the required crack pattern is formed all over a shaped part. Such microcracked chromium coatings have a slightly lower lustre than the thinner conventional chromium deposits and take longer to deposit. The improved resistance to... 

Concern over the health hazards of the hexavalent chromium solutions used to form the top coat of conventional nickel plus chromium coatings have encouraged research into trivalent chromium plating solutions. A process with better throwing power and improved covering power than those of hexavalent chromium has been described by Smart etal". A process for depositing a chromium-iron, or chromium-nickel-iron alloy, has been outlined by Law. ... 

When corrosion of a chromium-coated metal takes place, the corroding current concentrates its action on fissures in the deposit. There appears to be an incubation period, after which rapid attack occurs in the form of pits, and... 

Tin Free Steel—Electrolytic Chromium-Coated. A less expensive substitute for tinplate, electrolytic chromium coated-steel, has been developed and is designated TFS-CT (tin free steel-chromium type) or TFS-CCO (tin free steel-chromium-chromium oxide) (19). This material can be used for many products where the cathodic protection usually supplied by tin is not needed. A schematic cross section is shown in Figure 2. Electrolytic, chromium-coated steel is made by electro-lytically depositing a thin layer of metallic chromium on the basic tin mill steel, which is in turn covered by a thin passive coherent layer of chromium oxide. 

Douard, A., and Maury, F. (2006), Nanocrystalline chromium-based coatings deposited by DLI-MOCVD under atmospheric pressure from Cr(CO)6, Surf. Coat. Technol., 200, 6267-6271. 

A low deposition velocity in combination with a high vacancy supersaturation caused by the ion bombardment creates conditions for the intensive diffusion of aluminum atoms into a chromium coating. 

Until the 1970s, most chromium coatings had been applied (Table 10.11) by either electrodeposition or chemical vapor deposition. In the strip coating field vacuum [136] aud powder [137] coating and electrodeposition have been investigated extensively [138] since steel, having a thin flash coating of chromium, can compete successfully with tinplate. 

Sputtering has been used for many years to produce the chromium-coated photomasks that are often used in the production of glass microdevices. Recently, sputtering has become a common technique for the deposition of thin films in microfluidic and nanofluidic devices. For most applications, it is used as a convenient means for the production of patterned electrodes. However, as will be shown below, sputtering can be used to achieve far more than this. In the not so distant future, it is likely that the enormous versatility of this technique will be exploited for the fabrication of miniaturized fluidic devices with greatly enhanced functionality that would be difficult or impossible to produce by other means. 

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