Poly-4-vinylphenol conversion coatings

In the development of a reactive non-chrome post-treatment, a variety of phenolic resins were synthesized and commercial phenolic resins evaluated. It was found that phenol-formaldehyde resins, creso1-forma1dehyd e condensates, ortho-novo 1 ak resins, and phenol-formaldehyde emulsions gave positive results when employed as post-treatments over zinc and iron phosphate conversion coatings. The above materials all possessed drawbacks. The materials in general have poor water solubility at low concentrations used in post-treatment applications and had to be dried and baked in place in order to obtain good performance. The best results were obtained with poly-4-vinylphenol and derivatives thereof as shown in the following structure (8,9,10)... 

The quality observed with "Mannich" derivatives of polyvinylphenol is affected by the concentration, time of treatment, temperature, pH, and whether or not a final deionized water rinse is used. The results shown in Tables I-III below represent evaluations conducted for poly-[methy1(2-hydroxyethy1)amino]methyl-4-vinylphenol, as shown in Structure I. Post-treatments based on polyvinylphenols overcome deficiencies observed with previous chrome-free rinses, since these systems are reactive and a final water rinse actually improves performance as is illustrated in Table I where the new non-chrome system is evaluated on Bonderite 1000, an iron phosphate conversion coating, as a function of concentration with and without a final water rinse. It is also... 

The "Mannich" adduct synthesized from the condensation of formaldehyde, 2-(methylamino)ethanol and poly-4-vinylphenol as shown in Structure I, has been evaluated as a function of molecular weight versus corrosion resistance as measured by salt spray and humidity tests on Bonderite 1000, an iron phosphate conversion coating. The molecular weight of the polymer was varied from approximately = 2,900 to 60,000. The corrosion resistance results were essentially equivalent over the molecular weight range evaluated. 

On zinc phosphate conversion coatings, the "Mannich" derivatives of poly-4-vinylphenol have demonstrated performance equivalent to chromic chromate systems in salt spray, humidity, and physical testing. In addition. Table III illustrates results observed with automotive body paint systems evaluated by the "scab" or "cycle" test which causes failure more typical of actual end use conditions than do salt spray evaluations. Again, results equivalent to chromic-chromate post-treatments were obtained. In addition, the humidity resistance and adhesion tests were essentially equivalent to the chromium controls. 

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