Electrodeposition coating methods

Electrodeposition Coating Methods. A detailed description of electrodeposition is given by G. E. F. Brewer in a separate chapter of this book. In addition, a photograph of a commercial... 

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). 

Many of the finishes applied to other types of metal products can also be applied to zinc die castings, although some differences in formulation as well as occasional differences in method of application may be desirable. The types of finishes applicable to zinc die castings include mechanical finishes (buffed, polished, brushed, and tumbled) electrodeposited finishes (copper, nickel, chromium, brass, silver, and black nickel) chemical finishes (chromale, phosphate, molybdate and black nickel) and organic finishes (enamel, lacquer, paint and varnish, and plastic finishes). Electrodeposited coatings of virtually any metal capable of electrodeposition can be applied to zinc die castings. 

ISO 2179, Electrodeposited Coatings of Tin—Nickel Alloy, Specification and Test Methods, ISO, Geneva, Switzerland, 1986. 

Redepenning et al. developed a novel electrodeposition method of composite coatings of brushite (CaHP04-2H20) and chitosan on titanium to achieve an electrodeposited coating with material properties similar to bone [115]. They... 

Dip coating is one of the simplest and oldest coating methods. In addition to dipping in solvent- or waterborne paints, electrodeposition has become important for large-scale series production (Table 8.5). 

Electrodeposition [11,12], metal spraying [13,14], and physical vapor deposition [15] (see also Section 10.2.2.3) are coating methods in their own right. However, heat treatment of such coatings is often used to obtain better adhesion or different surface properties. 

Coating of the molding inside the compression mold, a method adopted from the US known as inmold coating (IMC) has provided a useful interim solution, albeit a complex one. The coating prevents the pores from rupturing. This method can also be used to render the surface conductive as a preparation for electrodeposition coating or electrostatic spraypainting. 

The use of blocked isocyanates has proved an important method for cross-linking cathodic electrodeposition coatings (see p. 109). The resin in such a coating might be the reaction product of a bisphenol A diepoxide (with az=4, see p. 176) and diethylamine ... 

Standard Method of Corrosion Testing of Decorative Electrodeposited Coatings by the Coirodkote Procedure... 

ASTM Standard B 380 Standard Method of Corrosion Testing of Decorative Electrodeposited Coatings by tbe Corrodkote Procedure, Annual Book of ASTM Standards, Vol. 03.02, ASTM International, West Conshohocken, PA, 2001. 

B 380 Method o1 corrosion testing of decorative electrodeposited coatings by the Corrodkote... 

Coating methods are electrodeposition, electroplating, physical vapor deposition (PVD), chemical vapor deposition, sputtering, spraying, and nitriding. 

Both constant-voltage and constant-current coating methods have been employed, the latter eliminating large current spikes that can occur on switching on the voltage and can cause problems with some resists at the beginning of electrodeposition. 

Meng et al. reported that flnorine-doped nano-HA coating on Mg-Zn-Ca alloy by pulse electrodeposition was dense and uniform than the conventional electrodeposition method. The potentiodynamic polarization experiment indicated that pulse electrodeposited coating effectively protects the material from corrosion (Fig. 15.9). They also found that pnlse electrodeposition coating induces precipitation of Mg, Ca and more effectively in comparison with... 

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