ASTM A153/A153M-16a pdf.Standard Specification for Zinc Coating (Hot-Dip) on Iron and Steel Hardware.
ASTM A153/A153M covers zinc coatings applied by the hot-dip process on iron and steel hardware. The hot-dip galvanizing process consists of parts being immersed in molten zinc for a sufficient time to allow a metallurgical reaction between iron from the steel surface and the molten zinc, resulting in the formation of Zn/Fe alloy layers bonding the coating to the steel surface.
5. Workmanship. Finish, and Appearance
5.1 The zinc-coated articles shall be free from LIflcOatCd areas, blisters. Ilux deposits, dross inclusions, and other types of projections that would interfere with the intended use of the articles, or other defects not consistent with good galvanizing practice.
5.2 The zinc coating shall be reasonably smooth and uniform in thickness.
Nom 2—Smoothness of surface is a relative term, Minor roughness that does not interiBre with the intended use of the part, or roughness that is related to the as-received (ungalvanhzed) surface condition of the part. shall not be grounds for rejection.
Nom 3—Since this specification is applicable to items that are centrifuged or otherwise handled to remove excess bath metal (see 1.2). irregular coating distribution is not normally encountered. Drainage problems. which manifest themselves as local excess coating thickness that would interfere with function or as edge tears or spikes that present a safety haiard because of their sharpness. are grounds for rejection under the terms of 5.1.
5.3 Embrittlernent is a potential condition of steel that is cold-worked, depending on such factors as the steel type (strength level, aging characteristics), thickness, degree of cold work, and galvanizing process. The galvanizer. the designer and the fabricator shall take precautions against embrittlement. The precautions to fabricate properly and prepare the mawrial for galvanizing to prevent embrittlement are described in Practice A 143/A 143M.
Note 4—Low service temperatures increase (he risk of brittle failure of all plain carbon steels including those which have been galvanized. This temperature embrittling effect varies with type of steel. The expected service temperature should thus be taken into account when selecting steels for galvanizing.
5.4 Malleable castings shall be of such composition as will preclude the possibility that they become embrittled by the galvanizing process. or they shall be either cooled from the anneal, or subsequently heat-treated so as to immunize them against embrittlement.
5.5 The zinc coating shall adhere tenaciously to the surface of the base metal.
7. Test Methods
7.1 Tests shall be made to ensure that the zinc coating is being furnished in accordance with this specification and as specified for the following:
7.1.1 Minimum coating weight Irnassi or minimum coating thickness in 4.3.
7.1.2 Finish and appearance in 5.1 and 5.2.
7.1.3 Embrittlement in 5.3 and 5.4.
7.1.4 Adherence in 5.5.
7.2 Average Weight [ Mass ] of Coating:
7.2.1 The average weight [mass] of the zinc coating shall he determined by weighing specimens after pickling and drying and again after galvanizing unless the method described in 7.2.2 is used. The number of specimens that are used to determine the average of an inspection lot shall be derived from Section 6.
Nom 5—This method does not take into acCoUflt the weight Iniassi of iron reacted from the article that is incorporated into the coating. It will thus underestimate coating weight [mass] by up to approximately 10 %. Base metal reactivity will affect the extent of underestimation.ASTM A153/A153M-16a pdf free download.