The thermodiffusion zinc (TDZ) coating, which is deposited in powder mixtures, can be used for protection of steel products, tubes and fasteners from corrosion in the atmosphere and corrosive media and for improvement of service characteristics of parts.
The method for deposition of the TDZ coating is virtually waste-free and provides a uniform coating on the whole surface of products. The coating is rough and is light-gray in color. It consists mainly of the iron-zinc d-phase containing 7 to 10% of iron. The corrosion resistance is 2 to 4 times higher than that of galvanized and hot-dip galvanized coatings.
The technology is characterized by the followingparameters:
• the coating is deposited on products made of common-quality carbon steel, quality structural carbon steel, lowa-lloyed steel or cast iron;
• The plating time to obtain a 15—30 µm thick layer is 1 hour at a temperature of 390-430оC;
• the corrosion resistance of zinc-plated products with 30 µm thick coatings is 25 years;
• thermodiffusion plating of products is realized in the industrial scale on batch operation installations.
ADVANTAGES
• The use of a superfine zinc powder for thermodiffusion zinc-plating of threaded parts improves the quality of galvanization and allows the consumption of the zinc powder to be decreased (as compared to the consumption of ПЦ-1 – ПЦ-4 zinc powders).
• With respect to the relevant British standard, the technology provides a two-fold reduction in the zinc powder consumption for 30 µm thick coatings.
• Raw materials are used in a closed cycle. The technology is free from gas and dust emissions to the atmosphere.
