Aluminium containers coatings

Processed cheese products Polyethylene/printing inks/polyester laminate Polypropylene container with an aluminium lid coated with an acrylic based resin on the food contact surface and with nitrocellulose resin on the external surface... 

Although there is little published in the academic literature in this area, there are a considerable number of relevant patents involving a wide variety of geometneal-shaped substrates These are usually fabneated from aluminium-containing alloys, such as Kanthal and Fecralloy, which may be coated with a catalytic layer, as desenbed in Section ni.B. The following examples illustrate the range of work done in this area. 

When aluminium containers are lacquered, the integrity of the coating can be conductivity tested using a copper electrolyte solution. Increased conductivity indicates a poor coating, and results can be referred to standard tables for acceptability. 

Uranium in metallic contact with the inside of the aluminium container would lead to a reaction which would cause blistering and eventual bursting of the can. To prevent this, both the uranium rod and the inside of the aluminium can were coated with a thin layer of graphite before assembly. A further problem was that contact between the slug of uranium and the can altered due to the differential expansion of the two materials, leading to a reduction in the rate of heat transfer from the slug to the can and the formation of local hot spots . The cartridges were therefore filled with helium to improve the heat transfer. When differential expansion occurred the helium filled the gap and ensured reasonable thermal conductivity. 

The aluminium absorbs the radiation, heats up and transfers the heat to xenon gas contained in the cell. As the temperature of the gas varies the curvature of a flexible mirror of antimony-coated collodion, forming a part of the cell, changes. Reflection of a light beam from this mirror, which is on the outside of the Golay cell, indicates its curvature and therefore the intensity of radiation absorbed by the cell. 

The metals most commonly used for water systems are iron and steel. These metals often have some sort of applied protective coating galvanised steel, for example, relies on a thin layer of zinc, which is anodic to the steel except at high temperatures. Many systems, however, contain a wide variety of other metals and the effect of various water constituents on these must be considered. The more usual are copper, brasses, bronzes, lead, aluminium, stainless steel and solder. 

The solution also contains a high concentration of zinc (as zincate), which is noble relative to aluminium. As metallic aluminium is exposed, it corrodes, reducing zincate ions and forming a coating of zinc ... 

Calorised and heat-treated mechanically-clad products have coating structures similar to hot-dip aluminised coatings, but the degree of alloying with iron is variable (Fig. 13.5). With Calorised products the surface layers usually contain 25-50% aluminium. 

Aluminium coatings are not favoured in atmospheres containing explosive mixtures because contact with rusty steel can cause incendiary sparking, and for this reason aluminium coatings are not used for protection of structures in coalmines (cf. CP 2008 1966). 

The non-toxicity of aluminium coatings and freedom from taste or taint means freedom from health hazards during application and provides hygienic finishes for contact with foodstuffs, e.g. baking tins, oven trays, containers. 

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