Coatings ISPC

Neuder H., Sizemore C., Kolody M., Chiang R., Lin C.T (2003), Molecular design of in situ phosphatizing coatings (ISPCs) for aerospace primers , Pwg. Org. Coat, 47,225. 

In order to study the formation of interfacial metal phosphate layers, the untreated bare CRS panels were mechanically polished to a mirror finish and used as coating substrates. The ISPC was applied on mirror-finished CRS and cured at 163°C for 15 min. The polymer layer on each panel was removed without damaging the interface by soaking the panel in tetrahydrofuran solvent. The interfacial metal phosphate layer was rinsed with deionized water, dried, and characterized by a Bruker Fourier transform infrared (FTIR) spectrophotometer model Vector 22 equipped with a Spectra Tech FT-80 grazing angle accessory. 

In cathodic delamination, the delamination rate of an organic coating under a cathodic potential depends upon the applied potential, electrolyte solution, and metal substrate (22,25). Cathodic delamination tests were conducted for all three commercial paints. As an example, Figure 5 shows the cathodic delamination plots of control alkyd enamel and water-reducible ISPC coated on bare CRS coupons. Curves Sa and 5b represent delamination area for the control alkyd enamel and the water-reducible ISPC formulation, respectively curves 5c and 5d are the respective plots of delamination current for the two formulations. The delamination test was conducted in a 3% NaCI solution the alkyd coated CRS coupon served as a cathode and was polarized at -I.IV versus a saturated calomel electrode. A significantly slower delamination rate was obtained for the ISPC formula (curve 5b) as compared to the control alkyd enamel (curve 5a). At 44 hours of delamination time, the entire painted area of the working electrode (almost 20 cm x 20 cm) for the control alkyd paint had been delaminated, whereas the delamination area of the water-reducible ISPC was only as little as 1 cm indicating a remarkable coating adhesion improvement for the alkyd ISPC painted on bare CRS coupon. 

The salt water immersion test (SWI) and the standard salt spray (fog) test (SS) were conducted for both ISPCs and control baking enamels applied on bare CRS, iron phosphated B-1000, and BD+P60 panels. The painted coupons of about 1.0 mil dry film thickness cured at 163 C for 15 minutes were X-cut through the film to the substrate and then either immersed in a 3% NaCI solution (SWI test) or subjected to a continuous salt-solution spray in a test chamber (SS test). After a specified duration of testing, the specimens were removed from the salt solution, and the coated surface was immediately dried. A DUCK brand tape (Manco, Inc., Westlake, OH) was applied over the X-cut and then removed, and the protective performance was... 

---