Rabu, 01 April 2009
Hot Dip Process
The Hot Dip Process
The galvanizing process consists of the following basic steps:
Oil and Grease Removal -- A hot alkaline cleaner is used to remove dirt, oil, grease and soluble markings. This process is known as caustic cleaning. This cleaning will NOT, however, remove epoxies, paint, and welding slag. Those contaminants must be removed by sandblasting, which we can arrange for you.
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Pickling -- A dilute solution of hot sulfuric acid is used to remove surface rust and mill scale to provide a chemically clean metallic surface, readying the metal for the hot-dip process. This portion of the process can take anywhere from 30 minutes to 1-1/2 hours, depending on the complexity or the thickness of the part.
Fluxing -- Your steel parts will pass through this flux (a zinc ammonium chloride solution), which floats on top of our zinc bath. The fluxing process removes oxides and is intended to prevent oxidation of the steel prior to the zinc coating. This flux is then pushed aside to ensure clean removal of the steel parts from the zinc bath.
Galvanizing -- This is where the steel actually gets the zinc coating. The steel is immersed into a bath of molten zinc, which is heated between 820 and 850 F. During the galvanizing process, the steel comes up to the bath temperature and the zinc metallurgically bonds to the steel, creating a series of highly abrasion-resistant zinc-iron alloy layers, topped by an impact resistant pure zinc layer.
Inspection -- The final step in the hot-dip process to ensure compliance with the specifications. Coating thickness, uniformity, adherence and appearance are evaluated. Electronic testing gauges are used to give quick and convenient measurements of the coating. Additionally, Certificates of Compliance can be issued to satisfy the acceptable workmanship.
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