AS/NZS 1214:2016 pdf free.Hot-dip galvanized coatings on threaded fasteners (ISO metric coarse thread series) (ISO 10684:2004, MOD).
4 Materials
4.1 Raw material of parts
4.1.1 Chemical composition
Materials as included in ISO 898-1 and ISO 898-2 are suitable for hot dip galvanizing except if the total content of phosphorus and silicon is between 0,03 % and 0,13 %, in which case high temperature galvanizing (530 °C to 560 C) is recommended.
4.1.2 Surface condition
The surface of the fastener, before immersion in the molten zinc, shall be clean and free from all contaminants that would adversely effect the galvanizing.
4.2 Zinc
The zinc used for this process shall be in accordance with ISO 1461.
5 Hot dip galvanizing procedures and precautions
5.1 Stress relief
Fasteners subjected to severe work hardening may require stress re’ief before acid cleaning and hot dip
galvanizing.
5.2 Cleaning and pickling
Parts shall be cleaned. During the cleaning process, hydrogen could be absorbed into the steel. The hydrogen may not effuse completely in the galvanizing bath and consequently. may lead to brittle failure. Unless otherwise agreed. parts heat treated or work hardened to a hardness of 320 HV shall be cleaned using an inhibited acid, alkaline or mechanical process. Immersion time in the inhibited acid depends on the as-received surface condition and should be of minimum duration.
NOTE An inhibited acid is an acid to which a suitable Inhibitor has been added to reduce corrosive attack on the steel and absoption of hydrogen.
5.3 Baking
If baking is carried out, it shall be carried out prior to surface activation.
5.4 Fluxing
Parts shall be surface activated, and dried if necessary.
5.5 Hot dip galvanizing
Normal temperature galvanizing is carried out at a bath temperature of 455 °C to 480 DC. High temperature galvanizing is used to produce a smoother and thinner coating and is carried out at a bath temperature of 530 °C to 560 °C. The finish obtained using the high temperature process is dull. In order to avoid micro- cracks, bolts, screws and studs of property class 10.9 in sizes M27 and above, shall not be high temperature galvanized.
Galvanizing shall not be carried out at bath temperatures between 480 °C and 530 °C.AS/NZS 1214 pdf download.