All “agricultural fencing” in the USA, consists of low carbon wire or high tensile wire. Low carbon wire is made from steel rod with an approximate 0.10% carbon content. While, this type of wire is easy to work with, it is prone to elongation (as in, stretching and sagging) and is weaker than high tensile wire. High tensile wire is made with steel rod which has approximately 0.28% carbon content.
The higher carbon content in high tensile wire significantly increases the wire’s strength and reduces elongation (stretching and sagging). Because of these improvements, it is possible to replace low carbon wire fencing with high tensile wire fencing of a smaller diameter.
A 12.5 gauge wire in high tensile would have a breaking load of nearly 1000 pounds (or more, depending on the psi rating), whereas, a 12.5 gauge low carbon wire would have a breaking load of 460 pounds. This would be as in comparing a 12.5 gauge high tensile wire with 12.5 gauge low carbon barbed wire.
High tensile fencing is easier to install because of its lighter weight and requires fewer posts during installation than low carbon fencing. When properly installed, high tensile fences require little maintenance and remain tight for years. Low carbon fences require regular maintenance and will stretch and sag over time.
The finish or coating of the wire will have a bearing on how long it will last. Class 3 Galvanized coating is the standard for most standard high tensile wire products. This coating is approximately 2.5 times thicker than the industry standard Class 1 Galvanized coating. Class I coatings are normally what is found on standard low carbon barbed or woven wires. Class III coatings will last three to four times longer than class I. There are also some new finishes available today such as the Zinc/Aluminum coating. This hybrid coating lasts more than twice as long as Class 1, but normally uses less coating than Class 3.
There is also a new painted finish becoming available; which combines a color polymer paint over a zinc/aluminum coated wire to give you longer fence life in attractive colors.
With high tensile fencing, you can build a longer lasting, lower maintenance fence for nearly half the price of a conventional low carbon fence.
The above article is a generalization, of wire properties, for farm fencing and written in layman terms as only a guideline for farm fencing. If you would like to read more technical information from a manufacturers point of view I would suggest going to http://www.bekaertwire.com/galvanizedwire.html. Bekaert is a wire manufacturer and their site gives a more complete description of the different coating processes that are currently being used worldwide.