Coagulation of polymer emulsions on metal surfaces

Emulsions of polyethylacrylate using sodium dodecylsulfate, cetylpyridinium chloride or nonylphenol ethoxylate as anionic, cationic and nonionic emulsifiers were prepared and the polymer deposition on metal panels in presence of an acid and an oxidizing agent was studied. Homogeneous films are formed within limited concentration ranges of the reactants. Diluted hydrofluoric acid and diluted hydrogen peroxide are useful components. Instead of a chemical oxidant a potential of 250 to 500 mV or more may be applied. The iron ion content of the film was determined by atomic absorption spectroscopy. A ratio of iron to emulsifier of 4.1 : 1 was found. The distribution of iron in film cross-cuts by scanning electron microscopy using the energy dispersive technique shows a high iron concentration near the metal interface and a sharp drop towards the film surface. In the outer third of the film the ratio iron to emulsifier is nearly 1 : 1. By adding iron salt solutions to polyethylacrylate emulsions the coagulation point was determined and a ratio iron ion to emulsifier of 1 : 1.2 was found in the coagulate. Steel panels were coated as well as phosphated steel or zinc but no film formation appeared on aluminum.