There are precautions provided in ASTM A/AM that should be considered to prevent embrittlement, as well as selecting steels with appropriate. Practice ASTM A provides guidance on safeguarding against warpage and be stress relieved per the guidelines provided within ASTM A, Section 6. ASTM A / AM Standard Practice for Safeguarding Against Embrittlement of Hot-Dip Galvanized Structural Steel Products and Procedure.
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However, the AGA does provide a compilation of specifications pertinent to galvanizing. Purchase a copy from the AGA, or contact your local galvanizer. 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. 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 specification requirements for coating thickness only contain minimums, there is no maximum coating thickness limitation in the specification.
Finally, the adherence requirement is for the entire coating to have a strong adherence throughout the service life of the galvanized steel.
ASTM A384 Recommendations
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 A, except for the addition of threaded products and embrittlement requirements.
A 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 A, for strong bond throughout the life of the hot-dip galvanized steel.
ASTM Specifications | American Galvanizer’s Association
The requirements in the specification facilitate the production of a high-quality zinc coating and are similar to those found in A and A 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.
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 A If rebar is bent fabricated after the galvanized coating is applied and any flaking or cracking occurs, it is not rejectable.
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. Common distorted and warped members of assemblies are sheets or plates assembled by welding or riveting.
The following can cause warpage and distortion: 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. 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. 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 A, A, A The specification outlines three acceptable forms of touch-up: See Specifying Duplex Systems for more information. 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.
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. 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. 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.
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.
It may also be known by its trade name, e. 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. 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.
This practice is applicable to chromate coatings of the colorless both one and two-dipiridescent 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. This specification covers prime western grade-recycled PWG-R zinc made by recycling zinc secondary materials including but not limited to drosses and skimmings.
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.
ASTM A Recommendations | American Galvanizer’s Association
The following is a summary of the various pertinent hot-dip galvanizing specifications. ASTM A 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, a1433 uncoated areas remaining after initial hot-dip galvanizing.
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