Terne is an alloy coating of lead and tin used to cover steel, in the ratio of 20% tin and 80% lead. Terne is used to coat sheet steel to inhibit corrosion. Steel is an Alloy consisting mostly of Iron, with a Carbon content between 0 Corrosion means the breaking down of essential properties in a material due to Chemical reactions with its surroundings It is the 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 minimise the cost.
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). You can still buy terne-coated steel at any roofing supply place. We do not use it because it's better to use terne coated STAINLESS steel (TCS), or copper, when replacing terne metal roofs. Both TCS and copper will outlast terne metal and don't need painted until they reach about 50 years (if ever). Terne metal needs painted immediately or it will rust and it has to be painted regularly. If it is kept painted, it will last a long time (90 years).
The latest version of terne is called terne II. It is an alloy of zinc and tin (the lead has been removed for environmental reasons). Tin is a Chemical element with the symbol Sn (stannum and Atomic number 50 The terne coated stainless is now called TCSII. It's available from Follansbee in Follansbee, WV.
I should add that when ordering terne coated stainless from a roofing supply company make sure you make it very clear that it's STAINLESS steel you're ordering. Numerous times we have been shipped terne coated steel instead of the terne coated stainless steel that we ordered due to salesmen who weren't too bright and didn't know the difference.
See also
- International Tin Council
- Tinning
- Cassiterides
- Tin pest
- Whisker (metallurgy) (tin whiskers)