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GALVANIZING
DESCRIPTION
BJCHI has built Thailand’s largest zinc galvanizing factory with the intent to accommodate the increasing galvanization demands of not only BJCHI’s Project but also other manufacturers in and out of Thailand. This factory possesses advanced air ventilation system to ensure safe operations, efficient production facilities to enhance the galvanizing quality, while reducing hazardous wastes to minimize impact to the environment.
STANDARDS
- ASTM A 123 (2000): Standard Specification for Zinc (Hot-Dip Galvanized) Coatings on Iron and Steel Products
- BS EN ISO 1461:1999: Hot-Dip galvanized coatings on fabricated iron and steel articles
- AS/NZS 4680: 2006: Hot-Dip galvanized (Zinc) coating on fabricated ferrous articles
- ASTM A153/A153M: Standard Specification for Zinc Coating (Hot-Dip) on Iron and Steel Hardware
GALVANIZING PROCESS
Surface preparation is the most important step in the application of coating. Failures in surface preparation will be apparent when the steel is withdrawn from the molten zinc.
A hot alkali solution is often used to remove organic contaminants such as dirt, paint markings, grease and oil from the metal surface. Grit–blasting, sand–blasting, or other mechanical means can also be used.
Scale and rust normally are removed from the steel surface by pickling in a dilute solution 18% by volume hydrochloric acid.
Fluxing removes oxides and prevents further oxidation on the metal surface , prior to galvanizing.
Fabricated items are immersed in the bath until they reach bath temperature. The zinc metal reacts with the iron on the steel surface to form a zinc/iron inter-metallic alloy.