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Galvanized Galvannealed

Steel with Zinc / Iron Coating

Its excellent ability to protect against corrosion and its high surface quality, make GALVANNEALED recommended for numerous applications in various market segments, mainly for the automobile industry in exposed or unexposed parts. The presence of iron in the coating gives it a particular adaptability for point soldering and is especially recommended when the assembly conditions are problematic with other types of coatings.

GALVANNEALED is obtained by the process of hot dip galvanizing in a continuous line (passage of the steel sheet through a bath of liquid zinc), a substrate that can be chosen from among a range of qualities of the cold rolled steels. After passing through the zinc bath, the steel sheet is subjected to a thermal treatment that causes the diffusion of iron from the substrate in the zinc coating. In this way a zinc/iron alloy is formed, containing about 10% iron and composes the coating. Its high surface quality (no irregularities with controlled texture) results, in industrial conditions, an appearance level of paint and applications for exposed use. Another extremely important characteristic of this coating, is that it is relatively hard, which can vary as a function proportionally to the various stages of the alloy formation, which is controlled by the domain of the process.

This hardness can cause a peeling risk of the coating during more intense stamping, particularly for thicker coatings. That is why we recommend thinner coatings when using Extragal.


Corrosion

It provides an excellent protection against corrosion, even in the case of damage (small shocks, scratches and impacts), thanks to the electrochemical behaviour of the pair iron/zinc. This protection is a little more durable than Extragal, when comparing equal coating thicknesses. This occurs due to a lower electrochemical potential of the coating combined with steel, permitting the use of thinner coating thicknesses to improve the stamping performance.

It provides an excellent protection against corrosion, even in the case of damage (small shocks, scratches and impacts), thanks to the electrochemical behaviour of the pair iron/zinc. This protection is a little more durable than Extragal, when comparing equal coating thicknesses. This occurs due to a lower electrochemical potential of the coating combined with steel, permitting the use of thinner coating thicknesses to improve the stamping performance.

It should be noted that in case of damage, the presence of iron in the coating gives the GALVANNEALED corrosion products a reddish colour, which should not be interpreted as a sign of substrate corrosion.


Stamping

It offers, in cases of stamping, superior performance to other coatings due to the low coefficient of friction, which facilitates the flow of metal between the master mold and the punch. The various types of lubrication (type of lubricant, quantity) and the texture of the product are of utmost importance during the sheet/tool contact. Any ranking of coatings can only be done under identical conditions.

The greater hardness of this coating (due to the presence of iron) can make its use more delicate in deep drawing stamping situations.


Soldering

It is the main advantage of GALVANNEALED. The hardness and the melting point of this coating make it a product whose solderability is similar to an uncoated sheet, especially with the excellent useful life of the electrodes. It presents a range of solderability suited to industrial requirements.

Design Foster Copyright 2007 - ArcelorMittal Vega do Sul