On a purchase order the three finishes sit one line apart and read as interchangeable. They are not. Picking wrong rarely fails a structure, since tie wire carries no design load once the concrete sets. It stains a finished face, slows a crew down, or costs more than the job needed.

What the three finishes actually are Black annealed

Low carbon steel wire heat treated, or annealed, to soften it. The dark grey to black surface is an oxide film left by that heat treatment, not a protective coating, and it will not stop rust. What annealing buys is ductility: the wire takes a tight bend and a hard twist without snapping. That is why it is the default for rebar tying and why powered tying tools are built around annealed wire.

Much black annealed wire also ships with a light oil film to hold off warehouse rust, and that oil transfers to hands, gloves and formwork. The black annealed coils in this catalogue are listed as an oil free, dry finish, so ask whether a competing quote is oiled.

Galvanized

The same steel core with zinc over it. Zinc is a physical barrier, and because it is less noble than steel it corrodes in preference to the steel wherever the coating is scratched. Tie wire is usually electro galvanized, a thin, even, bright coating; hot dip is heavier and dearer. A listing that says only galvanized does not tell you which, so ask if coating weight matters. Zinc also leaves the wire stiffer in the hand, and a crew hand tying all day will tell you so.

Stainless

An alloy, not a coating, so there is no layer to wear through. Chromium forms a passive film that reforms after it is scratched. Type 304, chromium and nickel, is the common general purpose grade. Type 316 adds molybdenum, which is what buys real resistance to chloride pitting: salt spray, deicing salt, pool and wastewater chemistry. Stainless work hardens as you twist it, so it feels springy and takes more effort per tie. Pin the grade down before you buy, because listings normally state the finish and not the alloy.

Corrosion in concrete, without the overstatement

Concrete is strongly alkaline, and that alkalinity passivates embedded steel. Black annealed tie wire buried at proper cover is not a durability problem. It is the default because it works, not because it is a compromise.

The trouble is the ends, not the buried wire

Rust bleeding through a finished face usually traces back to wire that never got cover: tails bent toward the form instead of back into the mat, ends snipped flush at the form face, offcuts left in the formwork before the pour. Nobody notices on a warehouse slab. On architectural concrete, a polished floor or a feature wall, that staining is the callback. Guidance on concrete surface defects treats wire left in the formwork as cosmetic rather than structural, which is true and no comfort to whoever explains it to the client. The fixes are crew discipline and stainless ties at the visible faces only.

Galvanized wire on black rebar is not the upgrade it looks like

Zinc is anodic to bare steel. Couple a small quantity of zinc coated wire to the large area of an uncoated rebar mat and the zinc gives way first. Galvanizers give the same advice from the other direction: tie galvanized bar with black wire and the zinc on the bar dissolves sacrificially around every tie to protect that bare wire. Match the tie to the bar.

Galvanized is not pointless, it needs the right reason. It belongs with galvanized reinforcement, and anywhere the assembly must survive before it is covered: cages fabricated weeks ahead of the pour, mats that sit through two weeks of rain, coastal and salted sites. Galvanized annealed tie wire runs here from half pound coils to 25 lb spools.

Stainless ties on carbon steel bar

Stainless is the more noble metal, so on paper it is the cathode and the carbon steel is at risk. In sound concrete it does not work that way: both metals sit passive in the alkaline pore water at closely similar potentials, so the driving voltage is small and the galvanic current negligible. Guidance on mixing stainless and carbon steel reinforcement generally finds no need for deliberate electrical isolation where both are cast into sound, chloride free concrete.

The caveat is chlorides, and it lands where stainless is most tempting. Where chloride reaches the level of both metals, or new stainless is tied to carbon steel already sitting in salted concrete, the carbon steel can corrode faster for having stainless attached. On a bridge deck, marine structure, parking deck or anything with a written corrosion durability requirement, that is the engineer of record's call and not a purchasing one.

Epoxy coated rebar is a different rule

Bare wire nicks epoxy at every contact point, and every nick is a hole in the barrier the owner paid for. Epoxy coated bar is normally tied with epoxy, plastic or nylon coated wire on coated or non conductive supports. Coated wire is not listed in this catalogue today, so ask for it by quote.

Where each one belongs

If a specification or the engineer names a wire or a corrosion requirement, buy that. The rest assumes nothing is specified.

• Interior slabs, footings, walls, anything covered and poured soon. Black annealed #16. The #16 black annealed 3.5 lb coil, about 340 ft is the standard working size.
• Cages or mats stockpiled outdoors before the pour. Galvanized, for storage and handling life rather than embedded durability.
• Exposed architectural or visible concrete. Black annealed with disciplined tails, or stainless at the visible faces where no staining risk is acceptable.
• Coastal, deicing salt, pool decks, wastewater, anything chloride heavy. Stainless, 316 rather than 304 where exposure is constant. Confirm the grade and the mixed metal question with the engineer first.
• Galvanized reinforcement. Galvanized tie wire. Never black ties on galvanized bar.
• Epoxy coated reinforcement. Coated tie wire. Ask before substituting.
• Temporary work: bundling, bracing, formwork, scaffolding. Black annealed in a heavier gauge than a rebar tie. The black annealed scaffolding tie wire in 100 lb coils is offered in #9 through #12.
• Still deciding, or trialling a finish. The 1 lb, 100 ft #16 coil comes in black annealed, galvanized or stainless, the cheapest way to put all three in a crew's hands.

Gauge and pack come last. #16, at 0.0625 in, is the standard rebar tie. #18 and #20 go further per pound and suit lighter tying, the sign trade and decorative work. #12 through #9 is bracing and scaffolding wire.

What the three cost WirePackPrice #16 black annealed3.5 lb coil, about 340 ft$16.49 #16 black annealed5 lb plastic spool$33.92 #16 black annealed5 lb metal spool$34.82 #16 black annealed or galvanized1 lb coil, 100 ft$11.65 #20 galvanized annealedhalf lb coil, 155 ft$6.19 #18 galvanized annealed3.5 lb coil$35.06 #18 galvanized annealed25 lb spoolfrom $88.16 Black annealed scaffolding wire, #9 to #12100 lb coil$539.10

Three things to read there. The gauges are not all the same, so this is not a clean coating against coating comparison: the 3.5 lb black annealed coil is #16 and the 3.5 lb galvanized coil is #18, a lighter wire that goes further per pound. Every price includes delivery, so a 1 lb coil carries the same freight as a 100 lb coil, which is why you compare pack against pack instead of reading a price per pound across pack sizes. And several listings carry options, the small coils by finish and the 25 lb spool by gauge, so take the price off the option in the cart rather than the headline. Stainless costs the most per pound as material, but on small delivered packs the three sit closer together than that implies.

Requirements for cover and corrosion protection vary by jurisdiction and by project specification, so nothing here replaces your local code or the engineer of record.

Ordering

Western Steel & Wire is the seller behind the tie wire above, on the Global Wire Exchange marketplace. Listed prices include delivery, so the number on the page is the number you pay and there is no freight to work out at checkout. The coils are listed to ASTM A853, the general purpose carbon steel wire specification, which is the reference to quote when a purchase order wants a standard named. For pallet quantities, a standing supply arrangement, a particular stainless grade or a coated wire that is not listed, send the requirement through our contact page for a quote.