Chromium oxide, lacquer adhesion

Composition of Surface Film and Adhesion of UVC Lacquer. As the deadhesion of UVC lacquer has occurred at the interface between the substrate and lacquer (or in the oil film), both chromium oxide and oil film affect the adhesion performance. From this standpoint, the adhesion of the UVC lacquer is summarized in Fig. 9. When chromium oxide is hydrated to a high degree or surface oil is oxidized to a greater level, the adhesion of the UVC lacquer does not deteriorate. 

Figure 9. Effect of the polar group ratio of oil and the hydration degree of chromium oxide on lacquer adhesion.

During prebaking for the internal coating, dehydration of chromium hydroxide (decrease in n-value) has occurred. If surface oil is oxidized at the same time, the adhesion loss of UVC lacquer due to the dehydration is made up for by the oxidation of the oil. 

The adhesion of UVC lacquer is likely to deteriorate in wicket-contact portions where the dehydration of chromium hydroxide occurs but only limited oxidation and vaporization of oil take place. 

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