Hot-Dip Galvanized Zinc Coatings on Fabricated Ferrous Articles

Standard Specification for Hot-Dip Galvanized Coatings to be used in conjunction with the Australian / New Zealand Standard 4680 and is designed for simple insertion into specifiers' overall materials specifications.

Scope

This specification covers the after fabrication galvanized coating applied to general steel articles, structural sections, angles, channels, beams, columns, fabricated steel assemblies, castings, threaded fasteners, steel reinforcement and other steel components.

This specification does not apply to the galvanized coating on semi-finished products such as wire, tube or sheet galvanized in continuous, semi-continuous or specialised plants.

Galvanizing

All articles to be galvanized shall be handled in such a manner as to avoid any mechanical damage and to minimise distortion.

Design features that may lead to difficulties during galvanizing should be pointed out prior to dipping.

Galvanizing parameters such as galvanizing temperature, time of immersion and withdrawal speed shall be employed to suit the requirements of the article.

The composition of the zinc in the galvanizing bath shall not be less that 98.0% zinc.

Coating Requirements

Thickness

The thickness of the galvanized coating shall conform with Table 1 and Table 2 in AS/NZS 4680:

The thickness of the galvanized coating shall first be tested by the purchaser/designer at the galvanizer's works, using an approved magnetic measuring device. In the event of any dispute, an independent test shall be carried out in accordance with AS/NZS 4680, Appendix G.

Table 1

REQUIREMENTS FOR COATING THICKNESS AND MASS FOR ARTICLES THAT ARE NOT CENTRIFUGED

Article Thickness mm

Local Coating Thickness

Average Coating Thickness

Average coating mass

Micron

Micron

g/m2

1.5mm or Less

35

45

320

Over 1.5 to 3mm

45

55

390

Over 3 to 6mm

55

70

500

Over 6mm

70

85

600

Table 2

REQUIREMENTS FOR COATING THICKNESS AND MASS FOR ARTICLES THAT ARE CENTRIFUGED

Article Thickness (incl. casting)  mm

Local Coating Thickness

Average Coating Thickness

Average coating mass

Micron

Micron

g/m2

Less than 8mm

25

35

250

8mm and over

40

55

390

Surface Finish

The galvanized coating shall be continuous, adherent, as smooth and evenly distributed as possible, and free from any defect that is detrimental to the stated end use of the coated article. On silicon killed steels, the coating may be dull grey, provided the coating is sound and continuous.

The integrity of the coating shall be determined by visual inspection and coating thickness measurements.

Where slip factors are required to enable high strength friction grip bolting, where shown, these shall be obtained after galvanizing by suitable mechanical treatment of the faying surfaces.

Where a paint finish is to be applied to the galvanized coating, this should be advised at the time of order and all spikes shall be removed and all edges shall be free from lumps and runs.

Adhesion

The galvanized coating shall be sufficiently adherent to withstand normal handling during transport and erection.

Source: Galvanizers Association of Australia

For more information on this source please visit Galvanizers Association of Australia

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