Standard and Specification of Galvanizing
Galvanizing is a process of coating steel or iron with zinc, whereby the surface layer of a metal structure is homegenized with zinc to form a corrosion protection layer. It is widely used in the construction, automotive and other industries. Galvanizing protects the surface of the metal from being attacked by air or water and prevents it from rusting or decaying. It also improves its appearance and helps in the easy operation of the component.
The galvanizing process is carried out by a galvanizer. It typically begins with the cleaning the metal surface with an etching solution that removes the oils and greases that may be present. The metal is then immersed in a bath of molten zinc and heated to around 750°F (400 °C). The zinc forms an alloying layer with the metal, creating a rust-proof layer.
The end result of galvanizing depends on a variety of factors, such as alloy composition and process parameters. The thickness of the galvanized layer on the metal surface depends on the concentration of zinc in the bath, the temperature, and the time of immersion.
The standard and specifications for galvanizing are determined by the American Galvanizers Association (AGA). The AGA prescribes stringent quality control measures for galvanizers, which are given in the publication Recommended Guidelines for Hot-Dip Galvanizing.
The AGA also provides guidelines for inspecting galvanizing work. The inspection process consists of three phases: acceptance, repair and examination. During the acceptance phase, the galvanizer records the various parameters such as galvanizing temperature, immersion time and thickness of zinc onto a certificate. During the repair phase, the galvanizer identifies any defects, such as pores or cavities, and takes corrective action. During the examination phase, the galvanizer inspects the products surface to ensure that the zinc coating meets the required standards.
In addition to the standards prescribed by the AGA, galvanizers must also adhere to the specifications of the ASTM International (formerly the American Society for Testing and Materials). The ASTM A123/A123M Standard specifies the requirements for paint coating, zinc coating, and thermal spraying of the external surface of products for their protection against corrosion.
To ensure that the galvanizing process adheres to the specifications of the AGA and the ASTM A123/A123M standard, galvanizers must take severe measures such as maintaining high-quality conditions in their workshops, testing the zinc baths regularly, and properly training the workers.
Galvanizing is an effective way of protecting the surfaces of metal products from corrosion. It is important for galvanizers to adhere to the high standards specified by the AGA and the ASTM A123/A123M standard to ensure that the galvanizing process is done properly. Following these guidelines will help galvanizers to manufacture galvanized products that provide long-lasting protection against corrosion.
