Tin-coated cans

Standard 0.25 or 0.50 lb (227 g) tin coated cans are used for packaging Hquid with neutral and mildly alkaline base formulas polypropylene is used for acid—base removers. Steel and polypropylene dmms are used for industrial removers. Viscous removers are packaged in removable top containers. Dry caustic removers are packaged in bag-lined boxes or fiber dmms. 

Molten tin wets and adheres readily to clean iron, steel, copper, and copper-base alloys, and the coating is bright. It provides protection against oxidation of the coated metal and aids in subsequent fabrication because it is ductile and solderable. Tin coatings can be appHed to most metals by electro deposition (see Electroplating). 

Tin-coated cans may deliver corrosive tin salts into foods, though inorganic tin does not appear to accumulate in living organisms. 

Steel parts because the deposition temperatures lies beyond the austenitizing temperature of steel. PVD-appliedTiN is also used for a variety ofrelatively higher melting point materials, such as stainless steels, titanium, and titanium alloys [197]. TiN coatings can also be deposited by thermal spraying, whereas TiN powders are produced by the nitridation of titanium with nitrogen or ammonia at 1200 °C [198]. 

In order to increase resistance of the container to the effect of the product or to protect the product from the tin plating, an inert, internal organic coating can be appHed. 

A similar coating, containing 4 wt % tin, is appUed to copper sheet and is used primarily for huilding flashings. Other lead—tin aUoys, usuaUy with 50 wt % tin, ate appUed as coatings to steel and copper electronic components for corrosion protection, appearance, and ease of soldering. Lead—tin aUoys can... 

Hot Dip Tin Coating of Steel and Cast Iron. Hot dipping of tin [7440-31 -5] has been largely superseded by electrolytic coating techniques, especially for sheet. However, hot dipping can be the method of choice for complex and shaped parts. Very thin layers of tin are extensively used to passivate steel used for canned goods. Tin is essentially nontoxic, is nearly insoluble in almost all foods, and easily wets and completely covers steel with a pinhole-free coating. 

The coating thickness may range from 0.0025 to 0.05 mm, depending on the type of protection required. Pure tin coatings are used on food-processing equipment, milk cans, kitchen implements, electronic and electrical components, fasteners, steel and copper wire, pins, automotive bearings, and pistons. 

The immersion deposit is necessarily somewhat defective, for the reasons already mentioned, though immersion deposits from complex ions are finer grained and more satisfactory than those reduced from aquocations. The zinc coating is, under the best conditions, an acceptable basis for a copper undercoat from the cuprocyanide bath, on which other coatings can be plated, but there is usually a fair proportion of rejects in commercial operation. Other processes similar in principle use tin or bronze immersion coatings. 

Fruit juices, meat products, milk and milk products, fish and most vegetables, in which tin is likely to be anodic to steel, can be handled open to the air in tinned steel vessels. Some corrosion of the tin occurs at rates similar to those found for pure tin and in due course retinning may be necessary. The alloy layer in hot-dipped tin coatings is cathodic to both tin and steel and, under aerated conditions may stimulate the corrosion of both metals, but this effect appears to be unimportant in practice. 

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