The Composition of Tin Cans

Tin cans have been used for food storage since the beginning of the 19th century. The cans provide an airtight container which enables the stored food to be kept without spoiling for months or even years, depending on the type of food. The cans also provide a solid outer casing which protects the contents while being transported.

Tinplate Steel

• Tin cans, since the beginning of their mass production at the start of the 20th century, have been made out of tinplate steel. These two metals together formed an ideal container for food storage, as they combine the strength and rigidity of steel with the corrosion resistance of tin. The material is nontoxic and recyclable.

Aluminum

• The use of aluminum in the design of the tin can initially started in 1957. Aluminum was used due to its similar corrosive resistance qualities to tin, but also its greater malleability. This makes the material easier to manufacture into the desired shape, requiring less energy and time to go into the production of cans. Aluminum also has a lower initial cost than steel.

Bisphenol A

• Bisphenol A, also known as BPA, is used to increase the corrosive resistance of tin cans. Normally used to create plastics and resin, BPA forms a thin plastic coating on the inside of the can. This prevents contact between the contents and the metal container, which in turn prevents corrosion of the metal or contamination of the food. In 2010, investigations began over BPA's potentially hazardous effects on tinned food. As of 2011, research is still being undertaken about its effect on pregnant women, infants and children. It is thought that developmental changes that have been seen in tests on animals could also similarly affect humans.

Recycling

• Tin cans are among the most commonly recycled food packaging items. Over 65 percent of steel cans are recycled. This is done by collecting sorted steel from homes and businesses and transporting it to a nearby recycling plant. The steel is then placed it into a furnace and molten iron is added. Oxygen is then blasted into the furnace, which heats up to over 1,700 degrees centigrade. The molten steel is poured into molds to create slabs of steel, which are rolled into appropriate shapes and sizes, dependent on their new use. Recycled steel can be used to form paper clips, cars or new food cans.