Metal packaging ranges from tin biscuit containers and aluminium to steel beverage cans. Metal is useful because it's durable, doesn't cost too much and is non-toxic, making it highly suitable for storing food. However, this kind of packaging also has a few disadvantages. Problems with metal packaging vary according to the specific type of metal used.
Some types of metal packaging, such as steel, are vulnerable to the effects of corrosion, which can cause the metal to deteriorate. Corrosion takes place as the metal begins to transform back into its original state; for example, steel turns back into the iron ore it came from. Corrosion is caused by oxidation, brought about when the metal is exposed to air and water. One example of corrosion is rust, which occurs on steel packaging and causes it to flake away. Metal packaging is typically coated in other materials, such as chromium, to prevent corrosion from occurring.
Can't See Contents
Metal packaging may keep a container's contents secure and fresh, but it does pose a disadvantage in that it is not transparent, and so consumers can't see into the packaging to check the contents or to further inspect a potential purchase. This limits the uses for metal packaging within the retail sector, since other packaging materials---such as plastic---are better in some situations. For example, the plastic used in a blister pack used to store nails allows consumers to check the size and type of nails inside the packaging, which wouldn't be possible with metal packaging.
Tin is often used for certain types of containers, including those for biscuits. Becuase the metal packaging isn't easily bent or squashed by hand, the containers are difficult to store effectively, both during and after use. On the other hand, a paper or plastic container might be easier to fold up or squash and tuck away in a cupboard or other storage facility.
Aluminium and Acidity
Aluminium is another common choice for metal packaging. While aluminium is impervious to corrosion when used to store food products, it does have an issue with acidic foods such as rhubarb and tomatoes. These foods are especially acidic and can be affected by aluminium if the metal is used to store them. The result of using aluminium packaging for these foods is that the food will end up tasting of aluminium.