Material galvanized to ASTM 123, ASTM 767or ISO 1461 are often indistinguishable even to a trained observer, and the coatings can be identical in metallurgical structure. ASTM 1094 will usually have a slightly brighter appearance due to a slightly higher percentage of aluminum than most other galvanizers use in their zinc bath.
There are, however, significant differences between the standards which should not be ignored. Foremost, ASTM 767 and ASTM 1094 require post treatment of the galvanized bar with a chromate solution. Both standards also require the galvanizer to maintain lot and mill heat identity and be able to provide complete traceability along with copies of the original material certifications with all shipments. The minimum required coating thickness for each of these standards is shown below.
There is no maximum coating thickness listed, but since both ASTM 1094 and ASTM 767 Class 2 are intended for fabrication after galvanizing, they should be kept under 4.5 mils to avoid problems. Interestingly, when a galvanized coating does crack or flake, the dis-bonding occurs between the Delta and the Zeta phase, leaving some zinc alloy beneath.
ASTM A 123 Standard Specification for Zinc (Hot-Dip Galvanized) Coatings on Iron and Steel Products is the proper standard for galvanizing accessories such as embeds and bearing plates and is not properly used for ordering reinforcing bars.
