blueBar = CGR + epoxy Advantage of the Product: Superior Corrosion Resistance Zinc coatings provide excellent corrosion protection by offering both barrier and sacrificial protection of the underlying steel. However, corrosion protection can be further enhanced by the addition of a paint or powder coat (epoxy) over the zinc coating. The resulting duplex corrosion protection system provides an additional barrier and slows down the rate at which the zinc is consumed – greatly extending the life of the zinc-coated steel. In return, the zinc greatly delays the corrosion of the underlying steel and subsequent peeling of the epoxy coating.  BlueBar is a trademarked name to distinguish a duplex system CGR product. The blue color was chosen to differentiate the product in the market of existing epoxy coated steel [green] and black bar (no protection). 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. It delays the corrosion of the underlying steel and subsequent peeling of the epoxy coating.  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 zinc-iron alloy layers, the coated bar can be bent, stretched, or twisted without cracking or flaking the coating, regardless of the total coating mass. This improves the formability of the epoxy coating that is bonded to the surface of the zinc layer. There is no zinc loss due to brittleness during forming in the field and repair requirements are minimal. 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 also has a standard for epoxy coatings on rebar (A775), "Standard Specification for Epoxy-Coated Steel Reinforcing Bars." The epoxy thickness required by this standard is 175-300 microns for 9.5 - 15.9mm and 175-400 microns for 19.1 - 57.3mm. The epoxy coating on blueBar iis applied pursuant to this standard. 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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