Tinplate lacquered

Tinplate for containers and closures is often decorated by colour printing and protected by clear lacquers. No surface preparation is carried out and difficulties with wetting and adhesion, sometimes associated with the character of the oxide layers on the surface, are rare. 

Meat Products. Laboratory investigations as well as practical experience have shown that aluminum containers do not cause the objectionable darkening of meat that occurs with other metals. Wunsche (13) found that luncheon meat stored in lacquered aluminum cans retained its normal color after more than one year, while a slight surface discoloration was observed on the same product packed in lacquered tinplate cans. 

Use In paints, alkyd resin enamels, printing inks, lacquers, rubber, resins, papers, tinplate printing, colored chalks, and pencils. 

Use Printing inks, especially for tinplate printing rubber plastics artist colors lacquers. 

Tinplate, with various types of base steel and coating weights. Since tin is now a high-cost material, lower coating weights are frequently supplemented by lacquers, enamels, print coverage to add to protection from potential corrosion. 

Metal containers are strong, relatively unbreakable, opaque, and impervious to moisture vapour, gases, odours and bacteria, providing they are pinhole-free. They are also resistant to both high and low temperatures. However, metals require the application of coatings and lacquers to prevent chemical reaction and corrosion from the inside or outside. Special coatings and coating techniques have therefore been developed for this purpose, e.g. tinplate is in fact a coated material. 

Both tinplate and aluminium sheet may be used to produce shallow drawn containers, the choice depending on cost versus product resistance. Dry products and nonaqueous creams are usually satisfactory in tinplate, whereas aqueous creams are better packed in aluminium. Alternatively, lacquered tinplate can be used for aqueous creams but there is always a chance of corrosion at any raw edges. Tinplate is stronger than aluminium for a given thickness. 

Metal—low carbon steel, tin coated, and aluminium, i.e. tinplate—corrosion protection can be improved by use of external enamels and internal lacquers. 

Tojdcdogy LD (oral, rat) > 15 g/kg, (IP, rat) > 3 g/kg TSCA listed Uses Pigment, colorant in paints, alkyd resin enamels, printing inks, lacquers, plastics, mbber, resins, paper, paper/wood coatings, finishes, sizing, textile lubrication, tinplate printing, colored chalks and pencils, hair dyes processing aid in latex foams pharmaceutical topicals colorant in food-contact polymers, paper/paperboard in contact with aq./fatty foods... 

Uses Pigment in paints, printing inks, emulsion paints, wallpaper, linoleum, carbon papers, student-grade artist materials, syn. resin lacquers, leather finishes, inks for foil and tinplate printing, paper coating and dyeing, typewriter ribbons, rubber, celluloid, cellulose acetate, P/F, U/F, styrene, protein plastics, and textile printing... 

A typical solvent blend for a vinyl rollercoating lacquer for tinplate is isophorone/Shellsol E or N 1/1. For paper MEK/MIBK/toluene 40/25/35. For spray applied vinylorganosol coating DIBK/Shellsol A /SBP-3 10/45/45. 

Cans are widely used to pack food. In some cases tinplated steel cans are used, for example, for packing fruit. Predominantly, the cans are internally coated with a polymeric coating to prevent corrosion or food spoilage. A considerable amount of work has been done in recent years investigating the extent to which compounds present in the lacquers migrate into food. 

Tinplate (or tin-free steel) cans offer a hermetic seal and the amount of oxygen present in the can after vacuum-sealing is usually not enough to cause oxidation problems. In addition, the can has a chemically reducing surface in the tin or an inert surface in the case of lacquered (enamelled) cans. In the case of acid foods the need for additives can be reduced by the presence of the lacquer. 

In carbonated beverages the potential reversal does not take place therefore, the steel dissolves preferentially at the defects in the tin layer. Under such conditions pitting corrosion sometimes results in perforation. Consequently, except for fruit cans almost all tinplate cans are lacquered. 

Alternating current scanning electrochemical microscopy (AC-SECM) was recently used to detect precursor sites for localized corrosion on lacquered tinplates (114). AC-SECM utilizes the effect of an increasing (decreasing) solution resistance as the SECM tip approaches an insulator (conductor) for mapping domains of different conductivity/electrochemical activity on surfaces immersed in electrolytes. It was demonstrated that AC-SECM could be used to visualize microscopic cracks and holes in the coating of the lacquered tinplates. 

Pournaras, A.V., Prodromidis, M.I., Katsoulidis, A.P, Badeka, A.V., Georgantelis, D., and Kontominas, M.G. (2008) Evaluation of lacquered tinplated cans containing octopus in brine by employing X-ray microanalysis and electrochemical impedance spectroscopy. J. EoodEng., 86,460-464. 

These products with an extended shelf life can normally be kept indefinitely (in practice about 5 years). Special can materials have to be chosen when the fish is canned with corrosive ingredients such as tomato or mustard sauce, vinegar or lemon juice. The can is usually made of a lacquer-coated tinplate or inert aluminum. 

Katemann, B. B., Inchauspe, C. G., Castro, P. A., Schulte, A., Calvo, E. J., Schuhmann, W. Precursor sites for localised corrosion on lacquered tinplates visualised by means of alternating current scanning electrochemical microscopy. /ecfroc/jZm. Acta 2003,48, 1115-1121. 

The internal coating is applied last by airless spray from static spray guns with an 80 millisecond burst of spray onto the inside of the spinning can. The can is then stoved, typically at 190-200°C for 60 seconds to 2 minutes peak metal temperature, upright in a flat bed conveyor oven. The tinplate can usually receives two coats of lacquer (wet on dry, i.e., each coat is stoved in turn), in contrast to the aluminium can which receives one coat of lacquer. 

---