Continuously Galvanized Rebar Advantages of the Product: The Corrosion Protection of Zinc The usual batch galvanized rebar (BGR) has a galvanized coating with a zinc metal layer overlaying thick iron-zinc intermetallic layers. Continuous galvanized rebar (CGR) has a galvanized coating that is more than 99% zinc metal. This increases the amount of unreacted zinc that is available to protect the steel rebar. Superior Coating Adhesion The CGR galvanized coating is joined to the steel rebar by a reaction layer approximately 0.1 microns thick. It is an FeAlZn layer rather than the ZnFe layers used in BGR that can be tens of microns in thickness. This FeAlZn layer is produced by adding a small amount of Al (0.2%) is added to the zinc bath. The thin FeAlZn alloy layer is the same as produced on continuously galvanized sheet and is very adherent and formable. The thin alloy layer remains about 0.1 microns thick for all masses of zinc over it and is not affected by the grade of steel substrate, i.e., reactive steels are not an issue with obtaining good adhesion. With no thick ZnFe alloy layers, the CGR can be bent, stretched, or twisted without cracking or flaking the coating, regardless of the total coating mass. There is no zinc loss due to brittleness during forming in the field and repair requirements are minimal. Superior Corrosion Resistance in Concrete The zinc passivation stage during concrete curing normally consumes about 1 micron of zinc but with CGR coatings there is always pure zinc under the passivation layer so the passivation stage could not consume all the pure zinc. Pure zinc reacts best with wet concrete to form an effective CaHZn passivation layer. CGR requires less zinc without compromising corrosion protection. Cost The cost of CGR is less than 20% above the cost of black rebar. Enforcing Standards: ASTM standards exist for hot-dip galvanized (HDG) rebar (A767/A767M). There is also an applicable ISO specification (14657) that defines thinner zinc coatings as compared to ASTM A767/A767M. ASTM is in the process of establishing a specification for CGR and CGR + epoxy titled: “New specification for zinc-coated (continuous hot-dip galvanized) steel bars for concrete reinforcement”. The standard, ASTM WK46112 is being developed by Subcommittee A01.05 on Steel Reinforcement, part of ASTM International Committee A01 on Steel, Stainless Steel and Related Alloys.  The new ASTM specification is out for ballot expected to be available in 2015. If you are interested in our production and need any additional information about them (e.g., related specifications, pictures etc.), please contact us.

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