Galvanizing is the steel wire transformation process of coating steel wire with zinc to prevent corrosion. Corrosion resistance will occur through 1) zinc being a physical barrier between the environment and the steel and 2) cathodic protection, where zinc acts as a sacrificial anode for steel.
Prior to the hot dip zinc coating process, the steel could undergo thermal treatment before acid cleaning. Achieving greater flexibility in mechanical properties (soft, medium, and hard temper). Then, within the hot dip process, an intermetallic layer of Fe/Zn is formed creating a strong metallurgical bond between steel and zinc. Afterward, forming lubricity and corrosion protection can be provided by coating the wire with a water-soluble wax.
Sivaco offers two coating processes, one of which can provide a zinc coating with 1.2 ounces of coating per square foot, and the other of which can provide 0.15 ounces per square foot. Zinc coated wires are produced by both processes in accordance with ASTM A641. In addition, a Galfan coating is available which offers three times more corrosion protection. Galfan is a zinc and aluminum alloy containing mishmetals that complies with ASTM B750.
Wire is one of the generic types of metallurgical products, together with plates, sheets, bars, tubes. Encyclopaediae generally define metallic wire as a “ single strand or rod of metal, usually cylindrical “. The history of wire making goes way back in Antiquity .
The first known writing relating to wire appears in the Bible (Ex.39:3): “ And they did beat the gold into thin plates, and cut it into wires...) However, archeological discoveries date the art of wire making to much earlier times, probably as far back as 4000 BC : a necklace containing gold wire was found in the tomb of an Egyptian Pharaoh who reigned about 2750 BC and there are wire-containing jewelry and ornaments made by Assyrians in the 1700's BC.
The manufacturing of wire was for a long time limited to jewelry and similar decorative items using “soft” materials such as gold or bronze. Utilitarian uses started to appear in the latter years of BC, as shown by 3 bronze wires twisted into a cable found in Pompei. For many centuries, wire was manufactured by hammering the ductile metals gold & bronze into thin sheets. Then hammers and files were used to transform the thin strips into short round pieces , which could eventually be brazed into longer wires . There is however evidence that even in the antique Egypt some wire were actually drawn through tapered holes , the crude predecessors of “dies”.
Modern wire manufacturing done by drawing through dies can be traced to the 300 AD to 700 AD period. Wire manufacturing by drawing through dies became common in the 12th to 14th centuries, in France, England and Germany: in those times, wire was drawn by hand. German wire manufacturers started to use waterpower to replace hand operation in the Middle Age. Also, German manufacturers of the Düsseldorf area discovered about 1650 the advantage of using lubricants (such as stale beer!) to draw hard steel.
Thus, the basic method of wire manufacturing, i.e. drawing a soft metal through a hard, incompressible die has remained unchanged for centuries. Obviously, modern industrial wire manufacturing has developed for productivity and quality a number of sophisticated technologies pertaining to:
- Wire rod (feed material coming from the hot rolling mill) quality and special coatings
- Drawing lubricants (Na or Ca based soap–type compounds)
- Diamond (oil drawing) or carbide dies (dry drawing) of increasing high technology
- Very productive highly automated multi-hole drawing machines
- Continuous processes combining cleaning, annealing, coating and skin pass sizing
The above narrative obviously only pertains to the “metallic wire” and not to the increasingly important glass wire involved in the “fiber optics” industry.