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Hot-dip Galvanization AASTHO

AASTHO (American Standards ASTM A-123)

Standard specifications for zinc coatings (hot-dip galvanization) on iron and steel products.

What does it consist of?

This specification covers the requirements for zinc coatings (galvanization) by the hot-dip process on iron and steel products consisting of rolled and forged profiles, castings, plates, bars and coils.

This specification covers both manufactured and non-manufactured products, for example, assembled steel products, steel
constructions, large tubes already bent or welded prior to galvanizing, and wire work fabricated from uncoated steel wire. This specification also covers steel forgings and iron castings incorporated into parts manufactured before galvanizing or that are too large to be centrifuged (or otherwise manipulated to remove excess metal from the galvanizing bath).

This specification covers those products previously mentioned in Specifications A 123-78 and A 386-78.

This specification does not apply to galvanized steel wire, pipes, tubing and sheet steel in special or continuous lines or to steel less than 22 gauge (0.0299 in.) [0.76 m] thick.

Galvanization of hardware

Galvanizing of hardware articles that must be spun or otherwise manipulated to remove excess zinc (such as bolts and similar threaded fasteners, castings, and rolled, pressed and forged articles) must comply with Specification A 153/ At 153M.
Assemblies manufactured from reinforced steel bars are covered by this specification. The galvanization of separate reinforced steel bars must be in accordance with Specification A 767/A 767M.

This specification is applicable to orders in either inch units (such as A 123) or SI units (such as A 123M). Inch units and SI units are not necessarily exact equivalents. Within the text of this specification and where applicable, SI units are shown in parentheses.

Each system must be used independently of the other without combining values ​​in any way. For orders in SI units, all tests and inspections must be carried out using the metric equivalent of the test or inspection method as applicable. In the case of orders in SI units, these will be determined by the galvanizer when the order is placed.

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Properties of the Coating

Coating Thickness – The average coating thickness for all controlled specimens must be in accordance with the requirements of Table 1 for the categories and thicknesses of the material to be galvanized. The minimum average coating thickness for any individual specimen is one coating class less than that required in Table 1. When galvanizing products consisting of multiple thicknesses or material categories, the coating thickness classes for each thickness range and category of material will be those indicated in  Table 1 .

In the case of orders in SI units, the values ​​in Table 1 will be applicable as metric units in micrometers. In the case of orders in inch-pound units, the measured value must be converted to coating class units using Table 2. The specification of coating thicknesses heavier than those required by Table 1 will be subject to mutual agreement between the galvanizer. and the buyer. (Figure 2 is a graphical representation of the sampling and specimen delineation steps and Figure 3 is a graphical representation of the steps in coating thickness inspection.)

Table 1. Minimum average coating thickness class by material category.
All controlled samples

Steel thickness range (measured) inches (mm)
Material category <1/16 (<1,6) 1/16 a <1/8 (1,6 a <3,2 1/8 a 3/16 (3,2 a 4,8) >3/16 a <1/4 (>4,8 a <6,4) ≥1/4 (≥6,4)
Structural plates and sections 45 65 75 85 100
Strip and Bars 45 65 75 85 100
Pipe and Tube 45 45 75 75 75
Wire 45 50 60 65 80

Table 2. Coating thickness class

Coating class milipulgadas onza/pie2 μm g/m2
35 1.4 0.8 35 245
45 1.8 1.0 45 320
50 2.0 1.2 50 355
55 2.2 1.3 55 390
60 2.4 1.4 60 425
65 2.6 1.5 65 460
75 3.0 1.7 75 530
80 3.1 1.9 80 565
85 3.3 2.0 85 600
100 3.9 2.3 100 705

Sampling

Sampling of each batch shall be carried out in accordance with the requirements of this specification.

A batch is a unit of production or shipment from which a sample may be taken for inspection. Unless otherwise agreed between the galvaniser and the purchaser or stated within this specification, the batch shall be as follows: For control at a galvanizing facility, a lot is one or more items of the same type and size from a single order or a single dispatch load, whichever is smaller or any number of items identified as a lot by the galvaniser when these have been galvanised within a single production shift and in the same bath. For inspection by the buyer after delivery, the batch consists of a single order or a single dispatch load, whichever is smaller, unless the identity of the batch, established in accordance with the above, is kept and clearly indicated on the shipment by the galvaniser.

The method of selection and number of control specimens shall be agreed between the galvaniser and the buyer. Otherwise, control specimens shall be selected at random from each batch. In this case, the minimum number of specimens from each batch shall be as follows:

Number of pieces in Number of specimens
3 or less all
4 a 500 3
501 a 1200 5
1201 a 3200 8
3201 a 10.000 13
10,001 and more 20

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