Zinc-iron alloy coatings

F == Iron rich zinc flash plating (Iron flash) ZnFe = Electrolytic zinc-iron alloy coated ZnNi Electrolytic zinc-nickel alloy coated Tough Coat (or TC) = Organic Composite Coating... 

The information on the corrosion resistance of the Zn/Fe alloy layers, either alone or in a zinc plus zinc-iron alloy coating system, is slightly conflicting, but the balance of data suggests increased corrosion resistance in acid atmo-... 

As compared with pure zinc, the zinc-iron alloy coatings provide increased corrosion resistance in acid atmospheres but slightly reduced corrosion resistance in alkaline atmospheres. 

To produce a zinc-iron alloy coating on iron or steel by keeping the coating molten after hot dip galvanizing until the zinc alloys completely with the base metal. 

Substantially all the zinc is absorbed by the surface of the components, and the resulting coating has a matt-grey appearance and consists essentially of a zinc-iron alloy averaging 90-95% Zn. If excess zinc is made available and the treatment is prolonged, pure zinc is deposited at the surface. 

Galvanize gal-v9- nlz (1802) v. To coat iron or steel with zinc by immersing in molten zinc to produce a coating of zinc-iron alloy. 

Adhesion Coating is integral with the steel because the formation process produces zinc-iron alloy layers overcoated with zinc. Good, comparable with other electroplated coatings. 

In an industrial atmosphere, the best results were obtained with electroplated iron-zinc alloy layers with more than 20% iron (Salt et al., 1965) with a corrosion resistance 30% higher than zinc. Elsewhere, zinc-iron alloy galvanized coatings were as good as coatings with an outer zinc layer. Sherardized coatings were superior to electroplated and equal to galvanized for the same thickness. However, the structure of the alloy layer affects the corrosion resistance, as does its composition. 

It is usually sufficient to differentiate only between small or medium salt contents—up to about 300 mg/L, as in drinking water and waters of higher salt contents. [Note that 1 mg/L = 1 part per million (ppm).] It is important to know whether the content is due to hardness-forming compounds alone or to other salts, and especially whether the chloride content exceeds about 50 mg/ L. The content of carbonic acid and of oxygen also is very significant. Microorganisms may accelerate or retard corrosion suspended solids such as sand usually are removed from industrial water before use the abrasion resistance of the zinc-iron alloy in coatings is helpful if suspended solids are present. 

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