Plasma polymer coatings corrosion test results

The corrosion widths of Prohesion salt spray-tested IVD Al-coated Al panels were calculated and are summarized in Figure 32.6. As is evident from the data, after 12 weeks of Prohesion salt spray testing, IVD/plasma polymer/spray paint systems showed better corrosion protection overall than IVD/plasma polymer/E-coat systems. All the IVD/plasma polymer/spray paint systems outperformed the cathodic E-coated controls and showed corrosion test results comparable to those of the Deft primer oated controls. 

The effect of interface of steel on the corrosion test result is summarized in Table 33.2. The results found for the panels, which were E-coated without phosphate or plasma polymer coatings, are quite astonishing. A scribe creep of 3.0 mm in a 4-week corrosion test was obtained for an oxide-removed CRS surface (without zinc phosphate nor plasma polymer), which is better than the E-coat on the... 

Figure 33.7 depicts the influence of plasma pretreatment of CRS surface as well as the hydrophilicity of the plasma polymers on corrosion test results. The left half of the bar graph represents hydrophilic interface and some of top surface are also hydrophilic. The right half of the bar graph represents the water-insensitive interface and nonhydrophilic top surfaces except the plasma polymer of CH4, which was intentionally kept in air for 10 min before application of E-coat. The figure indicates two important factors, i.e., the removal of oxides from CRS/plasma polymer interface, and nonhydrophilic top surface of plasma coatings, for corrosion protection of CRS by plasma interface engineering, which involves application of cathodic E-coat. While the air exposure of plasma polymer of CH4 severely deteriorated the corrosion protection of E-coated sample, the same exposure of TMS surface showed no effect. This difference seems to reflect the reactivity of double bonds described in Chapter 7. 

For the cyclic corrosion test, a layer of acrylosilane polymer coating (10-25 fim thick) was dip-coated onto the plasma-deposited substrates. The coated samples were then subjected to 25 scab cycles. The test results are plotted in Fig. 7. Corrosion performance (as described by the length of scribe creep) was correlated to the wattage used for plasma film deposition. As discussed in the previous section, the chemical structure and properties correlated with the deposition conditions, especially the power level applied. Therefore, atomic compositions for plasma polymers deposited at different power levels were also plotted in Fig. 7.A... 

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