Metal decorating coating systems

Decorative coatings of nickel plus chromium are cathodic to steel or zinc alloy substrates and with these protective systems deliberate use may be made of discontinuities in the chromium topcoat where corrosion of the underlying nickel will occur. If the number of these discontinuities in the chromium layer is greatly increased the current density at each individual corrosion site is reduced, penetration of corrosion through the thickness of the nickel layer is thus slowed down and the period of protection of the substrate metal is prolonged. 

Probably the most extensive coatings employed in electrochemical systems are passive films that are formed on metal and semiconductor surfaces (21,22). These anodic films are responsible for the corrosion resistance of reactive metals, such as Fe, Cr, Ni, Ti, Zr, Zn, Cu, Sn, and Al, among others, in aqueous environments as well as for the operation of various electrochemical devices (e.g., electrolytic capacitors). Decorative coatings on aluminum, titanium, and zirconium are also formed anodically, with those for aluminum being very highly developed. The principal limitation in the knowledge of the growth and... 

Chert). Descrip. Butoxymethyl methylol melamine (60%) in n-butanol Uses Crosslinking agent for alkyd/polyester or acrylic resins, for use in solv.-borne systems, industrial stoving finishes, automotive finishes, metal decorating and dipping enamels, polymeric/resinous food-contact coatings... 

Uses Crosslinking agent for TS acrylic and alkyd automotive top-coat finishes and metal decorating systems high resistivity for electrostatic spray finishes food-contact coatings, paper/paperboard Regulatory FDA 21CFR 175.300,176.170 Properties Sp.gr. 1.02 dens. 9.6 Ib/gal (solids) vise. 9-18 poises acid no. 1 max. flash pt. (Seta) 52 C 62 2% NV by wt. free formaldehyde (< 0.5% max.)... 

Many different decorative coatings and finishes may be applied to products fabricated of MAGNUM resins. Parts can also be readily metallized, plated, or molded with a grained, non-glare finish. Generally, non-aromatic based paint systems work well with MAGNUM resins. 

One of the reasons that water based coatings find limited usage in sheetfed systems is the difficulty of applying them by rollercoater methods, where they tend to give inferior film properties in comparison with solvent based ones. As the VOC is reduced, so the problems increase. Nonetheless, water based systems will gradually make inroads into the sheetfed metal decorating market. The high capital cost of incinerators necessary for VOC compliance in Europe and the USA will force may smaller operations either to use water based VOC compliant systems or close their operation. 

The other common alternatives to DMAE are triethanolamine and triethylamine. In contrast to many other water based systems, the amine does not need to evaporate at ambient temperatures. Indeed it is undesirable for this to happen. Metal decorating has the advantage, compared to many applications, that coatings are stoved at relatively high temperatures (typically up to 200°C). This allows lower volatility amines to be used. 

It may be possible to decorate or even to protect some surfaces with a single coat or finish, but protection of metal against corrosion always requires a finishing system. A full finishing system will require some or all of the following coatings. 

The technology for deposition from aqueous systems of metal on plastics was developed originally for acrylonitrile-butadiene-styrene (ABS), and it remains still the plastic used most widely in the field—particularly for the more traditional uses where the coating is essentially decorative. However, in the past decade requirements have changed and in response to this the range of plastics available for these processes has been extended. Some comments about the materials that are most important at present are given below. 

For some special applications as for instance electrode coating of oscillating quartz crystals, deposition of selenium films for electrical metal rectifiers and for dry copying systems, and for coating of a decorative incandescent lamps, special plants are fabricated. Fig. 67 shows such a lamp bulb coating unit. 

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