Coating defective

Many coating flows are subject to instabilities that lead to unacceptable coating defects. Three-dimensional flow instabilities lead to such problems as ribbing. Air entrainment is another common defect. 

The evaluation of At/ values together with off potentials are aids in deciding whether coating damage should be repaired. In addition, by comparison with previous results, intensive measurements indicate whether new coating defects have arisen. These could be the result of external foreign forces on the pipeline. 

Differences in rest potential can be about 0.5 V for cell formation with foreign cathodic structures. The danger increases on coated construction components with coating defects of decreasing size on account of the surface rule [Eq. (2-44)], and is limited, for a given soil resistivity p-Mv., not by the grounding resistance of the defect / , but rather by the pore resistance R2 and the polarization resistance of Rp. 

Standard of deposition such as thickness uniformity, or defined thickness variation and coating defects. 

Hsu, C. and Berger, P.D. "Surface Chemistry of Surfactants Used to Prevent Surface Coatings Defects," 1988 Symposium on Coatings Defects Federation of Soc. for Coatings Technol., Orlando, May 17-18. 

In all these cases we actually have not a "twofold-protection" but interdependent as well as ocmplementary mechanisms. The intact coating stem protect by its barrier action and, possible, 1 good wet adhesion, vhereas the electrochanical mechanism must be restricted to coating defects. 

In addition to the constraints mentioned above, active areas must be sufficiently long-lived and nearly fixed in position for detection by SVET. This is not normally a problem in the study of coatings where the location of active areas are often fixed by existing or emergent coating defects. However, some pitting phenomena, especially metastable pitting, may not be detected well by this technique. 

Ruotsalainen, M., Heinamaki, J., Guo, H., Laitinen, N., and Yliruusi, J. (2003), A novel technique for imaging film coating defects in the film-core interface and surface of coated tablets, Ear. J. Pharm. Biopharm., 56, 381-388. 

There are many coating defects that can degrade the sensitometiy. Film defects have been reviewed by Pierce and Schoff (1986). Drying-related defects can be frequently reduced by the use of surfactants to control the surface tension (Hansen and Pierce, 1974 Jerome, 1990). 

Unlike in the coater with steel belts, in this process equipment applicators such as wire-wound bars are nsed, which may be designed to rotate to assure a better, more uniform coating. The dip tanks are similar to those used in fabric coating, also nsing an immersed dip bar. To prevent coating defects due to shear, the dip tanks have double walls and are chilled by circulated chilled water to temperatures below 19°C (66°F), the hrst-order transition temperature. 

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