Terne
Encyclopedia
Terne is an alloy
coating that was historically made of lead
and tin
used to cover steel
, in the ratio of 20% tin and 80% lead. Currently, lead
has been replaced with the metal zinc
and is used in the ratio of 50% tin and 50% zinc..
to inhibit corrosion
. It is one of the cheapest alloys suitable for this, and the tin content is kept at a minimum while still adhering to a hot-dipped iron sheet, to minimize the cost.
Terne metal must be painted. If the paint is maintained, terne metal can last 90 years or more. Terne coated stainless steel (TCS) or copper is commonly used to replace terne metal roofs as either material will outlast terne metal. TCS or copper roofing can last 50 years or more unpainted.
Terne II uses zinc
in place of lead for environmental reasons. The new terne coated stainless is called TCSII.
Terne-coated steel is also known as terne-metal and often referred to as "tin" (see the Slate Roof Bible). Terne-coated steel can still be purchased at most roofing supply stores.
Alloy
An alloy is a mixture or metallic solid solution composed of two or more elements. Complete solid solution alloys give single solid phase microstructure, while partial solutions give two or more phases that may or may not be homogeneous in distribution, depending on thermal history...
coating that was historically made of lead
Lead
Lead is a main-group element in the carbon group with the symbol Pb and atomic number 82. Lead is a soft, malleable poor metal. It is also counted as one of the heavy metals. Metallic lead has a bluish-white color after being freshly cut, but it soon tarnishes to a dull grayish color when exposed...
and tin
Tin
Tin is a chemical element with the symbol Sn and atomic number 50. It is a main group metal in group 14 of the periodic table. Tin shows chemical similarity to both neighboring group 14 elements, germanium and lead and has two possible oxidation states, +2 and the slightly more stable +4...
used to cover steel
Steel
Steel is an alloy that consists mostly of iron and has a carbon content between 0.2% and 2.1% by weight, depending on the grade. Carbon is the most common alloying material for iron, but various other alloying elements are used, such as manganese, chromium, vanadium, and tungsten...
, in the ratio of 20% tin and 80% lead. Currently, lead
Lead
Lead is a main-group element in the carbon group with the symbol Pb and atomic number 82. Lead is a soft, malleable poor metal. It is also counted as one of the heavy metals. Metallic lead has a bluish-white color after being freshly cut, but it soon tarnishes to a dull grayish color when exposed...
has been replaced with the metal zinc
Zinc
Zinc , or spelter , is a metallic chemical element; it has the symbol Zn and atomic number 30. It is the first element in group 12 of the periodic table. Zinc is, in some respects, chemically similar to magnesium, because its ion is of similar size and its only common oxidation state is +2...
and is used in the ratio of 50% tin and 50% zinc..
Usage
Terne is used to coat sheet steelSteel
Steel is an alloy that consists mostly of iron and has a carbon content between 0.2% and 2.1% by weight, depending on the grade. Carbon is the most common alloying material for iron, but various other alloying elements are used, such as manganese, chromium, vanadium, and tungsten...
to inhibit corrosion
Corrosion
Corrosion is the disintegration of an engineered material into its constituent atoms due to chemical reactions with its surroundings. In the most common use of the word, this means electrochemical oxidation of metals in reaction with an oxidant such as oxygen...
. It is one of the cheapest alloys suitable for this, and the tin content is kept at a minimum while still adhering to a hot-dipped iron sheet, to minimize the cost.
Terne metal must be painted. If the paint is maintained, terne metal can last 90 years or more. Terne coated stainless steel (TCS) or copper is commonly used to replace terne metal roofs as either material will outlast terne metal. TCS or copper roofing can last 50 years or more unpainted.
Terne II uses zinc
Zinc
Zinc , or spelter , is a metallic chemical element; it has the symbol Zn and atomic number 30. It is the first element in group 12 of the periodic table. Zinc is, in some respects, chemically similar to magnesium, because its ion is of similar size and its only common oxidation state is +2...
in place of lead for environmental reasons. The new terne coated stainless is called TCSII.
Terminology
The term "nonterne" is frequently used to refer to substances or materials that do not contain terne or have not had terne used in their creation, as in the expression "nonterne-plated oil filters".Terne-coated steel is also known as terne-metal and often referred to as "tin" (see the Slate Roof Bible). Terne-coated steel can still be purchased at most roofing supply stores.
See also
- International Tin CouncilInternational Tin CouncilThe International Tin Council was an organisation which acted on behalf of the principal tin producers in Cornwall and Malaysia to buy up surplus tin stocks to maintain the price at a steady level....
- TinningTinningTinning is the process of thinly coating sheets of wrought iron or steel with tin, and the resulting product is known as tinplate. It is most often used to prevent rust....
- CassiteridesCassiteridesThe Cassiterides, meaning Tin Islands , are an ancient geographical name of islands that were regarded as situated somewhere near the west coasts of Europe...
- Tin pestTin pestTin pest is an autocatalytic, allotropic transformation of the element tin, which causes deterioration of tin objects at low temperatures. Tin pest has also been called tin disease, tin blight or tin leprosy ....
- Whisker (metallurgy)Whisker (metallurgy)Metal whiskering is a crystalline metallurgical phenomenon involving the spontaneous growth of tiny, filiform hairs from a metallic surface. The effect is primarily seen on elemental metals but also occurs with alloys....
(tin whiskers)