Tube and Struture Galvanizing Chemicals

The importance of protecting from corrosion articles used in open environment made of plain steel, such as structures and tubes etc., is obvious, and coating the steel surface with a thin layer of a corrosion resistant metal is a most convenient means of protection, best applied as a final operation in the manufacture of these products. Of all the metals used for the purpose of protection against corrosion, zinc is one of the cheapest and the one most widely used, being suitable for nearly every kind of article, except food containers. Use of zinc is not only cheaper and easy to coat but it also protects iron or steel by providing cathodic or sacrificial protection.

Mainly steel tubes / structures are galvanized in this method.

Degreasing – Removing oil, grease and dirt from steel is crucial to good galvanizing. Without this process acid pickling will be disturbed and a patchy zinc coating will form after galvanizing.

Ferrous metals have a surface coating of metallic oxide or scale which must be removed before the zinc coating can be applied successfully. The most common process for removing this film is called pickling. Pickling involves immersing the work in an acid to dissolve the scale or oxide film. Many acids can be used; the most common for galvanizers is hydrochloric acid.

A property of the preflux bath is that it makes a thin coating on metal surface which prevent further rusting and at the time of galvanizing it removes the oxide layer from the surface and confirms the zinc metal adhesion.

Zinc is also a sensitive metal which forms white rust on exposure to air and moisture. The corrosion products give an unsightly, mottled surface consisting of the loose powder that makes it unfit for the industrial and domestic uses. White rust damages long-term protection of the base steel. Passivation of the galvanized surface is inevitable for long life of the articles.