Paint Application

Electrodeposition This method of paint application is basically a dipping process. The paint is water-based and is either an emulsion or a stabilised dispersion. The solids of the paint are usually very low and the viscosity lower than that used in conventional dipping. The workpiece is made one electrode, usually the cathode, in a d.c. circuit and the anode can be either the tank itself or suitably sized electrodes sited to give optimum coating conditions. The current is applied for a few minutes and after withdrawal and draining the article is rinsed with de-ionised water to remove the thin layer of dipped paint. The deposited film is firmly adherent and contains a minimum of water and can be stoved without any flash-off period. This process is used for metal fabrications, notably car bodies. Complete coverage of inaccessible areas can be achieved and the corrosion resistance of the coating is excellent (Fig. 14.1). 

Pressures to reduce atmospheric pollution, increase safety in the workplace, and save energy have all influenced, paint application methods in... 

PAINT APPLICATION METHODS Table 14.1 Summary of process limitations... 

Although rolling and dipping are sometimes used, power spray painting is the usual method of paint application. Among the coatings used are polyurethane, epoxy, acrylic, alkyd and vinyl based paints. With paints that are oven cured, products must have sufficient heat resistance to survive without distortion, etc. 

After paint application, all coils are cured in an oven. Curing temperatures depend upon basis material, conversion coating, paint formulation, and line speed. Typical temperatures range from 93°C to a maximum of 454°C. Upon leaving the oven, the coils are quenched with water to induce rapid cooling prior to rewinding. 

Formulations which do not contain lead chromate are becoming increasingly important, not only for automotive finishes, but also for architectural paints and other areas of paint application. 

Initially, these lakes were precipitated onto inorganic carrier materials. It is interesting to note that this group of colorants was originally used for pigments in paints. Application in the textiles market followed later. Today, it is mainly the calcium and barium salts, but also manganese and, less frequently, strontium salts that have the largest sales volume. 

Due to its good opacity, the pigment is recommended in general industrial paint applications for lead- and cadmium-free formulations. 

For a specific paint application, a mixture of solvents is needed. The mixture is going to be identified by its ability to mix with water (total miscibility), normal boiling point (determines the solvent evaporation rate), the solubility parameter (determines if it is soluble in the paint) and molecular weight (size the candidate molecule). 

Ground calcium carbonate, extracted from the earth, is present in practically every country in the world in varying quantities in the form of limestone, marble, dolomite or chalk. Following the extraction, GCC needs to be ground. Dry grinding, the cheaper alternative, is often limited to a minimum particle size of 2- 3 microns. Wet grinding, more expensive, is used for fine and ultra fine material or when the final product must be a slurry (paper or paint application). Precipitated calcium carbonate is produced by chemical reaction between... 

Liquid form Extra precautions with electrostatic paint applications systems Limited material compatibility for delivery systems Can exhibit high water permeability Pigment flocculation... 

The wastes generated during paint application are primarily due to 1) paint overspray, and 2) the failure of the application which requires the stripping, cleaning, and repainting of the item. Source reduction can be achieved by use of low overspray application equipment, proper operator training, preventive maintenance, and parts inspection. 

Use of paint application equipment with low overspray characteristics. When comparing different types of paint application equipment, the transfer efficiency, the efficiency with which paint is applied to the object, can vary considerably. The lower the transfer efficiency, the higher the waste. 

Paint application equipment - spray guns, hoses, as well as brushes and rollers is often cleaned with solvents. Cleaning wastes can sometimes be recycled in ways such as (Lorton 1988) ... 

The risk of cancer among consumers and professional painters from the inhalation of 2-butanonoxime during paint application and drying was considered to be a concern. 

Because of the challenging environment in which ultrafiltration membranes are operated and the regular cleaning cycles, membrane lifetime is significantly shorter than that of reverse osmosis membranes. Ultrafiltration module lifetimes are rarely more than 2-3 years, and modules may be replaced annually in cheese whey or electrocoat paint applications. In contrast, reverse osmosis membranes are normally not cleaned more than once or twice per year and can last 4-5 years. 

Paint Application. Figure 2 illustrates and identifies the relative position of the bulkhead and overhead paint systems Figure 3 likewise identifies the deck paints. Only the navy formulations, paint systems 1 to 6, were evaluated in this trial. Samples 1, 3,4, and 6 were brushed on the bulkheads and overhead and samples 2,4, and... 

Titanates are valuable in other paint applications. Corrosion-resistant coatings have been described for tinplate, steel, and aluminum (440—444). Incorporation of phosphoric acid or polyphosphates enhances the corrosion resistance. Because titanates promote hardening of epoxy resins, they are often used in epoxy-based paint (445). Silicones (polysiloxanes) are often cured by titanates. Pigments, eg, Ti02, Si02, Al O and Zr02, are frequently pretreated with titanates before incorporation into paints (441,446). In these applications, the Ti(OR)4 compounds are often mixed with Si(OR)4, Al(OR)3, Zr(OR)4, and other metal alkoxides (12). 

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