No, most rebar is not galvanized. Standard reinforcing bar is plain, uncoated carbon steel, known in the trade as black bar, made in Canada to CSA G30.18 and in the US to ASTM A615 or A706. Galvanized rebar is ordinary black bar that has been hot-dip coated in zinc, and it only shows up on a job when the drawings or specification call for it. If your bar is dark grey with a film of orange rust, it is black bar, and that is normal.
What "black bar" means
Black bar gets its name from the dark mill scale that forms on the steel as it cools after rolling. It is sold bare, with no paint, zinc or epoxy, and it rusts lightly almost as soon as it sits outside. That is why rebar in a yard or on a site nearly always looks rusty.
That light rust does not matter once the bar is cast in. Fresh concrete is strongly alkaline, and in that environment a thin passive layer forms on the steel that keeps it from corroding. As long as the concrete is sound and the bar has the cover the drawings call for, black bar lasts for the life of most buildings. Our post on whether rebar rusts in concrete explains what breaks that protection down: chlorides from road salt, carbonation over many years, cracks and thin cover.
That is also why black bar is the default for footings, foundation walls, slabs on grade, columns and most beams. Coatings are reserved for exposures where the concrete alone is not expected to keep corrosion away for the design life.
How to tell if rebar is galvanized
You can usually tell at a glance, and the paperwork confirms it.
| Check | Black bar | Galvanized bar |
|---|---|---|
| Colour | Dark grey to black, often with orange-brown surface rust | Dull silver-grey, sometimes with a crystalline (spangled) pattern |
| After weathering | More rust | White or grey powdery film, little or no red rust |
| On the drawings | Bar callout only, such as 15M@250 | Often marked with a prefix, such as G15M@250, plus a specification note |
| Specification | CSA G30.18 bar | Zinc coating standard, typically ASTM A767 (or A1094 for continuously galvanized bar) |
| Tags and paperwork | Standard bar tags and mill certificates | Coating certification and re-attached tags |
The rolled-in markings on the bar (mill, size and grade) do not tell you whether it is coated; they are rolled in before any coating goes on. The Reinforcing Steel Institute of Canada (RSIC) Manual of Standard Practice suggests marking specialty bars on contract drawings with a letter prefix, G for galvanized, C for epoxy-coated, S for stainless and F for fibre-reinforced polymer, so check the drawing legend if a callout has a letter in front of it.
Do not confuse galvanized rebar with the zinc-coated tie wire, chairs or welded wire mesh that sometimes come with it. Galvanized mesh and galvanized tie wire are common products; galvanized bar is not.
Galvanized vs regular rebar
| Black (regular) rebar | Galvanized rebar | |
|---|---|---|
| What it is | Uncoated carbon steel bar | Black bar with a hot-dip zinc coating |
| Corrosion protection | From the concrete only | Zinc barrier plus sacrificial protection at small scratches, on top of the concrete |
| Where it is used | Almost everything | Exposed, salt-affected or thin-cover elements, precast and architectural concrete |
| Fabrication | Cut and bent any time | Usually cut and bent first, then galvanized (ASTM A767); continuous-process bar can be bent after coating |
| Laps and bends | Per CSA A23.3 and the drawings | RSIC practice treats bends and laps the same as black bar |
| Supports and ties | Standard chairs and tie wire | Non-corrosive chairs and zinc-coated or non-metallic tie wire |
| Ordering | Stock item | Specialty item, quoted separately |
A few of those points matter on site:
- The bar list has to be final before galvanizing. With batch galvanizing, bars are fabricated first and then dipped, so late changes mean new bars. The RSIC manual also notes that paper tags do not survive the acid cleaning before galvanizing, so the fabricator and galvanizer have to re-tag the bars.
- Keep galvanized and black bar apart. The RSIC manual calls for galvanized bars to be electrically separated from dissimilar metals in the concrete. Whether any black bar can touch galvanized bar in the same element is a design decision; ask the engineer rather than deciding on site.
- Repair damage. Cut ends and chipped spots get a zinc-rich repair coating, done to ASTM A780.
For a deeper comparison of the two common coatings, see galvanized vs epoxy-coated rebar. The specification details, including coating classes and bend requirements, are in our post on galvanized rebar specs.
Does galvanized rebar rust?
The short answer is that the zinc corrodes so the steel does not, at least for a long time.
- In storage, fresh galvanized bar left wet and poorly ventilated can develop white storage stain, a powdery zinc corrosion product. It looks alarming but is cosmetic in most cases. The RSIC manual notes that galvanized bar can be stored outdoors without hurting its corrosion protection.
- In concrete, the zinc forms a stable layer and tolerates more chloride than bare steel before it starts to corrode. Where the coating is scratched, the surrounding zinc corrodes first and protects the exposed steel.
- Over decades in a severe exposure, the zinc is slowly consumed. Once it is gone, the steel underneath behaves like black bar. Coating thickness, concrete quality and cover decide how long that takes.
So galvanized rebar is not rust-proof, and it is not a substitute for good concrete and proper cover. It buys margin. For elements where corrosion would be very costly, engineers also look at stainless steel and GFRP bar, which our guide to types of rebar in Canada compares.
Is Grade 60 rebar galvanized?
"Grade 60" is a US strength grade under ASTM A615 or A706: a minimum yield strength of 60,000 psi, which is 420 MPa. It says nothing about coating. Grade 60 bar is black bar unless the order says otherwise, exactly like Canadian bar.
In Canada the equivalent conversation is about 400W (and 400R or 500W), the CSA G30.18 grades. 400W is the common grade on Ontario jobs: 400 MPa minimum yield, weldable chemistry. It is close to Grade 60 but not identical, so a substitution between the two needs the engineer's approval. Our guide to Canadian rebar grades covers the differences.
When galvanized bar is specified, the order has two parts: the base bar (for example 15M, grade 400W to CSA G30.18) and the coating (the zinc standard and coating class). Both should be on the drawings or in the specification.
Welding is a separate issue. Welding through zinc gives off fumes and damages the coating around the weld, so galvanized bar that has to be welded needs a procedure for it. See can you weld rebar for how coated bars are handled.
When galvanized rebar is worth specifying
Black bar is the right answer for most buildings. Galvanizing tends to earn its place where:
- Concrete is exposed to de-icing salt or seawater and the element is hard to repair: balconies, exterior stairs and landings, parking structures, bridge elements.
- Cover is thin and cracking or staining would be unacceptable, as in precast panels and architectural concrete.
- Bars sit exposed for a long time before they are cast in, such as staged or phased work.
- The owner's specification already requires it, as some municipal and institutional specs do for particular elements.
It is rarely worth it in a basement wall, interior slab or footing, where good concrete and the code-required cover already protect black bar. Whatever the exposure, the decision belongs to the engineer of record, and it should be written into the drawings or specification before the bar list is prepared. For what goes into a galvanized rebar quote, see galvanized rebar price in Canada.
Ordering black or galvanized bar
We detail, cut, bend and tag black rebar from 10M to 55M to your bar lists and deliver across the GTA and Ontario. We supply black steel and GFRP bar; if your specification calls for galvanized bar, confirm the coating requirements with your designer before you order.
Send us your drawings and specification for a free take-off and quote, or see our rebar products.
Frequently asked questions
Is all rebar galvanized?
No. Standard rebar is uncoated carbon steel, called black bar, and it is what goes into the vast majority of footings, walls and slabs. Galvanized rebar is a separate product that has to be specified and ordered.
Is Grade 60 rebar galvanized?
Not unless it is ordered that way. Grade 60 is a US strength grade (60,000 psi, or 420 MPa), not a coating. Galvanizing is applied to ordinary bar after it is made, so a galvanized bar has both a base-bar grade and a zinc coating specification.
Does galvanized rebar rust?
The zinc corrodes slowly instead of the steel, which is how it protects the bar. Over a long time in a harsh exposure the zinc is gradually used up, and the steel underneath can then corrode. In storage it can form a white powdery stain, which is zinc corrosion, not rust.
Why is rebar always rusty?
Because ordinary rebar is uncoated, so it rusts lightly in the yard and on site. Light, tight surface rust is acceptable; loose flaking rust, mud and oil are not. Once the bar is cast in sound concrete with proper cover, the alkaline concrete protects it.
Is galvanized rebar better than regular rebar?
It resists corrosion better, which matters in exposed elements with salt or thin cover. In a basement wall or footing, black bar in good concrete performs well, so galvanizing adds cost without much benefit. The engineer decides based on the exposure.
