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Hot-dip galvanization UNE EN ISO 1461

General Galvanizing. What is it? What does it consist of?

Hot-dip galvanizing is the process of immersing finished steel-iron pieces in a furnace or bath of molten zinc at 450ºC. The objective of galvanizing is to prevent oxidation – corrosion that humidity and environmental contamination can cause on the metal, but what we really obtain with this procedure is an interaction between the metal and the molten zinc, creating on the piece alloys between these two elements which protect against corrosion in the most effective way.

But it is important to highlight that  the result is an alloy, not a coating. Thanks to this procedure we obtain a much more resistant material, with a more durable finish and protected exceptionally well from oxidation. Today, it is the most durable solution against corrosion.

This activity represents approximately 50% of zinc consumption in the world and for over 150 years it has been established as the most reliable and economical procedure for protecting steel against corrosion.

European and international Regulations

The European and international standard UNE EN ISO 1461, is the standard applicable to coatings obtained in discontinuous hot-dip galvanizing installations on various pieces and articles made of iron, steel, cast iron, etc.

In the UNE EN ISO 1461 standard, hot-dip galvanization is defined as the coating of zinc on iron and steel products by immersing these products in a bath of molten zinc, after preparing their surface
General Description

This standard recognizes that the chemical composition of the steel, the mass of the pieces themselves and the galvanizing conditions can influence the appearance, thickness, texture and physical/mechanical properties of the galvanized coatings obtained on the pieces in general galvanizing facilities.

This standard also requires that the galvanizing bath contain molten zinc with a total content of other alloying elements or impurities (excluding iron and tin) not exceeding 1.5% by mass. Likewise, the standard indicates in its annexes the information to be mutually provided between the client and the galvanizer to obtain the best results in terms of the quality of the coatings obtained and the economy of galvanization.

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Hot-dip galvanizing Process

The hot-dip galvanizing (HDG) process consists of several stages: bleeding, pickling, rinsing, fluxing and galvanizing, cooling, passivation, quality inspection, packaging and shipping.

The standard requires that a control sample be taken at random from each batch of galvanized materials to verify the thickness of the coating. The attached table specifies the minimum number of items to be included in the control sample in relation to the number of items in the inspection batch. It also indicates that, unless otherwise agreed, inspections of galvanized materials must be carried out before said materials leave the galvanizing plant.

The thicknesses of the hot-dip galvanized coatings obtained in galvanizing facilities on iron and steel pieces are proportional to the thicknesses of the material to be galvanized, as long as the galvanizing conditions are the same. Therefore, the attached table shows the requirements of the UNE EN ISO 1461 standard regarding mass and/or thickness of galvanized coatings on pieces that are not centrifuged after galvanization (medium and large sized pieces).

Galvanization composition

The composition of hot-dip galvanized coatings is made up of an external layer of pure zinc and several internal layers of zinc-iron alloys metallurgically bonded to the base metal and can be even harder than steel. These coatings have very interesting mechanical properties, that are: such as.

  • High resistance to abrasion.
  • High impact resistance.
  • Therefore, the standard indicates that it is not normally necessary to carry out coating adhesion tests on galvanized materials, since these are normally capable of withstanding handling consistent with their applications without any peeling or flaking of the coating.

If the client requests it, the galvanizer must issue a certificate in accordance with the requirements of the UNE EN ISO 1461 standard (in accordance with ISO 10474).

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