Coating quality

A steady-state rocket-type combustion spray unit has been developed, called high velocity oxy fuel (HVOF), that creates a steady state, continuous, supersonic spray stream (1.2—3 mm dia) resembling a rocket motor exhaust. The portable device injects and accelerates the particles inside a barrel (rocket nozzle). It produces coating quality and particle velocities equal to the D-gun at 5—10 times the spray rate with significantly reduced coating costs. 

A more recent development is the short dwell coater Beloit Short Dwell). The coater consists of a captive pond just before the blade that limits the contact time between sheet and coating material as shown in Fig. 6. The back flow assists in removing the boundary layer of air coming in with the sheet. The shorter contact time results in less coating penetration. Superior coating quality and improved runnability, due to fewer web breaks, have been achieved. 

SEM or TEM is a useful tool to investigate the micrograph of the electrodes surfaces. The image of the electrode can give us some information about the coating quality and implied some service-life information. For those nanometers, they also can imply some information about the crystal sizes. 

Coating quality Porous to dense, possibly Uniform, excellent imperfect Dense, excellent... 

DC cathodic polymerization of TMS mixed with argon improved the primer adhesion performance of the closed system TMS plasma polymers. Moreover, the addition of a certain amount of argon into the TMS plasma system further increased the plasma coating quality, reflected in the increase in refractive indices. Based on the higher compatibility with the IVD process, the excellent adhesion performance, and the benefit of one process combining TMS plasma polymerization and the postdeposition plasma treatment, DC cathodic polymerization of TMS mixed with argon in a closed system is being considered as a more realistic and favorable approach in practical applications. 

Conversion of the 1 2 complex to the 1 1 complex by oxygen or water results also in the production of undesired decomposition products, reducing the specific conductivity, cathodic limiting current density, and throwing power, and thus reducing the coating quality. 

A number of authors describe significant improvements in the polymer coating quality obtained by pulsed plasma polymerisation cf. CW). If these claims are substantiated, it would seem likely that research effort will focus increasingly on this mode of plasma deposition. The question arises as to whether the pulsed environment is simply an extrapolation of the low power CW environment, or whether it represents an entirely different plasma environment altogether. 

The main features of studies on this topic are summarized in Table 3. Because deposition of active metals in protic media is always accompanied by the hydrogen evolution, it is common to use substrates with a high hydrogen overpotential, to optimize solution pH, or to operate in aprotic solvents. Thus precursors of bismuth and thallium-based HTSCs are prepared most advantageously in aqueous media, while it is preferable to deposit Y-Ba-Cu and related compositions from organic media. In the latter case, traces of water can substantially spoil the coating quality... 

The primary requirement is to adjust the thermal expansion coefficients of the frit and enamel to that of the metal. For this purpose and for the necessary corrections, use is mostly made of additive factors. In view of the imperfections involved in such calculations, the main criterion is always the laboratory test the enamel is applied on a metal specimen and fired to assess the resulting coating quality. 

Figure 15 Over potential along pipelines with different coating qualities of...

Different metals may need different types of electrolyte. The composition and properties of the electrolyte is very important for the coating quality. 

The coating quality [1,21,42-47] was in fact negatively affected in the presence of bubbles by the development of void defects. An intriguing hypothesis explained these defects as negative fingerprints of the bubbles, created by their dynamic coating with a metal overlayer. Such a mechanism occurred on a short timescale and for small bubbles that is why, as we mentioned, it could not be easily observed before the advent of real-time coherent microradiology. 

---