ASTM’s copyright does not allow the AGA to include full-text versions of the listed specifications online. However, the AGA does provide a compilation of specifications pertinent to galvanizing. Purchase a copy from the AGA, or contact your local galvanizer.
The following is a summary of the various pertinent hot-dip galvanizing specifications.
- ASTM Main Standards
- ASTM Pre-Galvanizing Design Supporting Specifications
- ASTM Post-Galvanizing Supporting Specifications
- Other Specifications
ASTM Main Standards
Standard Specification for Zinc (Hot-Dip Galvanized) Coatings on Iron and Steel Products covers individual steel pieces as well as assemblies of various classes of material. The material categories covered in the specification include structural steel and plate, strips and bars, pipes and tubing, and wires. Fabrications can have more than one material category, such as a frame assembly. Any combination of these products can be assembled into a single fabrication and then hot-dip galvanized.
It is the responsibility of the designer and fabricator to ensure the product has been properly designed and built before the hot-dip galvanizing process (supporting specifications). The galvanizer’s responsibility is to ensure compliance with the specifications as long as the product has been designed and fabricated in accordance with the referenced specifications. However, if the galvanizer has to perform additional work in order to prepare the product for hot-dip galvanizing, such as drilling holes to facilitate drainage or venting, the galvanizer will communicate and resolve the issue with the customer.
The requirements listed in ASTM A123/A123 M include coating thickness, finish, appearance, and adherence. The specification requirements for coating thickness only contain minimums, there is no maximum coating thickness limitation in the specification. The finish requirement is continuous, smooth, and uniform, while appearance requires no uncoated areas or issues that interfere with the fabrication’s intended use. Finally, the adherence requirement is for the entire coating to have a strong adherence throughout the service life of the galvanized steel.
Standard Specification for Zinc Coating (Hot-Dip) on Iron and Hardware applies to hardware products such as castings, fasteners, rolled, pressed, and forged products, and miscellaneous threaded objects that will be centrifuged, spun, or otherwise handled to remove the excess zinc. The requirements of this specification are very similar to those in A123, except for the addition of threaded products and embrittlement requirements.
A153 requires a continuous, smooth, and uniform finish with no uncoated areas (including on the threads) or issues that interfere with its intended use. There are coating thickness minimums, but no maximums, and the threads are not subject to the coating thickness requirement. The adherence requirement is the same as A123, for strong bond throughout the life of the hot-dip galvanized steel. Finally, A153 contains information that high strength fasteners (>150ksi) and castings can be subject to embrittlement. There are precautions provided in ASTM A143/A143M that should be considered to prevent embrittlement, as well as selecting steels with appropriate chemistries.
Standard Specification for Zinc-Coated (Galvanized) Steel Bars for Concrete Reinforcement is exclusively applicable to hot-dip galvanizing of reinforcing steel bars, known as rebar, both smooth and deformed (wire is excluded). The requirements in the specification facilitate the production of a high-quality zinc coating and are similar to those found in A123 and A153. The requirements for finish, appearance, and adherence are identical to those in the other main standards. However, there are a few additional requirements for galvanized rebar. First, the specification details the coating thickness requirements based on bar size. Also, A767 outlines the galvanizer’s responsibility for consistent material tracking and identity. Finally, there are requirements for passivating the material (chromating) to prevent reaction between concrete and the zinc coating, and on bend diameters. Rebar is commonly bent prior to galvanizing, and the recommendations for diameter and best practices are provided in A767. If rebar is bent (fabricated) after the galvanized coating is applied and any flaking or cracking occurs, it is not rejectable.
ASTM Pre-Galvanizing Design Supporting Specifications
Standard Practice for Safeguarding Against Embrittlement of Hot-Dip Galvanized Structural Steel Products and Procedure for Detecting Embrittlement covers procedures to safeguard against the possible embrittlement of steel hot-dip galvanized after fabrication, as well as test procedures for detecting embrittlement. Embrittlement is the loss or partial loss of ductility in a steel where an embrittled product characteristically fails by fracture without appreciable deformation. Types of embrittlement commonly encountered with galvanized steel are related to aging phenomena, cold working, and absorption of hydrogen. The design of the product and selection of proper steel for its suitability to withstand normal galvanizing operations is the responsibility of the designer and fabricator.
ASTM A384/A384 M
Standard Practice for Safeguarding Against Warpage and Distortion During Hot-Dip Galvanizing of Steel Assemblies details best design practices to avoid warpage and distortion during the hot-dip galvanizing process. Common distorted and warped members of assemblies are sheets or plates assembled by welding or riveting. The following can cause warpage and distortion: use of nonsymmetrical sections such as channels; use of checkered plate; not properly vented overlapping joint for two pieces of steel; and too large assembly for a particular galvanizing kettle.
ASTM A385/A385 M
Standard Practice for Providing High-Quality Zinc Coatings (Hot-Dip) provides details on steel selection and other design practices such as venting and draining, welding, etc. to ensure the best quality product after galvanizing. Assemblies should consist of elements of similar chemistry and surface condition. Whenever different analyses of steel or different surfaces of steel are united in an assembly the galvanized finish is not generally uniform in appearance. All fabricated assemblies shall be designed with vent and drain holes such that no air is trapped during immersion of the assemblies into cleaning solutions or molten zinc.
Standard Practice for Life-Cycle Cost Analysis of Corrosion Protection Systems on Iron and Steel Products provides the equation and technology to perform a life-cycle cost (LCC) analysis of various corrosion protection systems. The LCC analysis considers not only the initial cost of the system but also the future costs (maintenance, replacement, etc.) The purpose of the calculation is to provide justification for the purchase of a higher initial cost system with a low life-cycle cost over an initially less expensive coating which has high future costs.
ASTM Post-Galvanizing Supporting Specifications
Practice for Repair of Damaged and Uncoated Areas of HOt-Dip Galvanized Coatings covers appropriate methods used to repair damaged hot-dip galvanized coatings on hardware, structural shapes, and other hot-dip galvanized products, including uncoated areas remaining after initial hot-dip galvanizing. Requirements concerning the renovation of uncoated areas after initial hot-dip galvanizing are contained within the material specifications (A123, A153, A767). The specification outlines three acceptable forms of touch-up: zinc-based solders, zinc-rich paints, and metallizing, as well as the required coating thickness of the repair.
Practice for Preparation of Zinc (Hot-Dip Galvanized) Coated Iron and Steel Product and Hardware Surfaces for Painting. See Specifying Duplex Systems for more information.
Practice for Preparation of Zinc (Hot-Dip Galvanized) Coated Iron and Steel Product and Hardware Surfaces for Powder Coating. See Specifying Duplex Systems for more information.
Standard Practice for Measuring Coating Thickness by Magnetic-Field or Eddy-Current (Electromagnetic) Examination Methods. Eddy-current-type thickness measurement is a non-destructive test measuring variations in the impedance of an eddy-current inducing coil caused by coating thickness variations. They can only be used if the electrical conductivity of the coating differs significantly from that of the substrate.
Other Related Specifications
Specification for Structural Steel. This specification covers carbon structural steel shapes, plates, and bars of structural quality for use in riveted, bolted, or welded construction of bridges and buildings, and for general structural purposes.
Specification for Cold-Formed Welded and Seamless Carbon Steel Structural Tubing in Rounds and Shapes. This specification covers cold-formed welded and seamless carbon steel round, square, rectangular, or special shape structural tubing for welded, riveted, or bolted construction of bridges and buildings, and for general structural purposes. This tubing shall be produced in both welded and seamless sizes and must have the chemical requirements of carbon, manganese, phosphorus, sulfur, and copper.
Specification for Hot-Formed Welded and Seamless Carbon Steel Structural Tubing. This specification covers black and hot-dipped galvanized hot-formed welded and seamless carbon steel square, round, rectangular, or special shape structural tubing for welded, riveted, or bolted construction or bridges and buildings, and for general structural purposes.
Standard Specification for Carbon and Alloy Steel Nuts. This specification covers the chemical, mechanical, and dimensional requirements for eight grades (Grades O, A, B, C, D, DH, C3, and DH3) of carbon and alloy steel nuts for general structural and mechanical uses on bolts, studs, and other externally threaded parts. Steel materials and nuts shall be manufactured, processed, and formed as appropriate for their respective grades.
Specification for High-Strength Low-Alloy Columbium-Vanadium Steels of Structural Quality. This specification covers the standard requirements for Grades 42, 50, 55, 60, and 65, of high-strength low-alloy columbium-vanadium structural steel shapes, plates, sheet piling, and bars for applications in bolted, welded, and riveted structures in bridges and buildings. It may also be known by its trade name, e.g. Exten (USS0
Standard Test Method for Comparing Bond Strength of Steel Reinforcing Bars to Concrete Using Beam-End Specimens. This test method deals with the standard procedures for establishing the relative bond strength of steel reinforcing bars in concrete using beam-end specimens. This test method shall determine the effects of surface preparation or condition (such as bar coatings) on the bond strength of deformed steel reinforcing bars to concrete.
Specifications for Steel Structural Shapes for Use in Building Framing. This specification covers rolled steel structural shapes for use in building framing or bridges, or for general structural purposes. Heat analysis shall be used to determine the percentage of carbon, manganese, phosphorus, sulfur, vanadium, nickel, chromium, molybdenum, columbium, and copper for the required chemical composition.
Standard Specification for Zinc. This specification covers zinc metal made from ore or other material by a process of distillation or by electrolysis in five grades as follows: LME grade, special high grade, high grade, intermediate grade, and prime western grade.
Standard Practice for Testing Chromate Coatings on Zinc and Cadmium Surfaces. This practice is applicable to chromate coatings of the colorless (both one and two-dip), iridescent yellow or bronze, olive drab, black, colorless anodic, yellow or black anodic types, and of the dyed variety, when applied to surfaces of electrodeposited zinc, mechanically deposited zinc, hot-dipped zinc, rolled zinc, electrodeposited cadmium, or mechanically deposited coatings.
Specification for Prime Western Grade-Recycled Zinc. This specification covers prime western grade-recycled (PWG-R) zinc made by recycling zinc secondary materials including but not limited to drosses and skimmings.
Standard Specification for Zinc Coating, Hot-Dip, Requirements for Application to Carbon and Alloy Steel Bolts, Screws, Washers, Nuts, and Special Threaded Fasteners. This specification covers the requirements for hot-dip zinc coating applied to carbon steel and alloy steel bolts, screws, washers, nuts, and special threaded fasteners applied by the hot-dip coating process.