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Industrias Duero, leaders in galvanizing and anti-corrosion treatment of steel. We have 63 years of experience in the sector, contact us.
From General Galvanization to thermo-lacquering, through Centrifugal Galvanization, Metallization, our experts are at your disposal to propose the best anti-corrosion and/or aesthetic solutions.
We have furnaces up to 14 (L) x 2.2 (W) x 3 (H) m.
The In Europe, hot dip galvanizing coatingson iron and steel articles are regulated by standard EN ISO 1461. However, under customer request, we can also galvanize under AASTHO specifications, or any other standard that is required.
When buying iron or steel to be galvanized, make sure you inform your supplier that the materialmust be appropriate for galvanizing, as not all steel qualities are suitable for this purpose.
If the iron or steel are not suitable for galvanizing, it often leads to reactivity problems (high concentrations of silicon and phosphorus in the chemical composition, causing the Zn to laminate in layers, or even wash away due to the absence of a proper zinc-steel alloy). Colours on the finished part may also appear dull and faded which, although it does not alter the corrosion resistance of the coating, it worsens the appearance of the products and increases the total cost for the customer, as the absorbed Zinc layer tends to become thicker.
The quality of the steel used in the parts to be galvanized, can be laboratory tested in a direct and simple way, by analysing a sample material in a tube-test with a mass spectrometer. In order to avoid costly and unpleasant surprises in your projects, be sure to verify your steel fabrications are suitable for galvanizing. Check all this and use steels suitable for galvanizing to avoid surprises in your projects.
The 2 previous points are valid for any type of steel, but when it comes to pieces cut by laser cutting, the client must take into account that some cuts leave scales on the edges that remain as a coating that is not lost in the galvanizing processes. easily removed, therefore the recommendation is to laser cut these pieces using nitrogen instead of oxygen(this is totally effective) or once the piece is cut, it goes over the edges to remove those scales.
The crucible of a galvanized is at a temperature of 450º C. When inserting a part, tensions accumulated in the manufacturing processes can be released and as a result, deformations sometimes occur, especially in large parts. To avoid this, the recommendation is to carry out welding with a procedure of welding frequencies, the same welding conditions and the same welding beads, so that we balance the tensions and they will not be released in the galvanizing. There are also other means to stabilize the pieces but this is the most economical.
In the manufacture of welded pieces it is necessary to eliminate the scales or projections produced by the welds, since they are stuck to the surfaces and will produce roughness imperfections and lack of a good finish in the galvanizing after galvanizing. The pieces must come as clean as possible. .
In the case of flat surfaces with a large surface in contact with each other, discontinuous welding must be avoided, if the contact gap is very narrow, since Zn does not enter the overlap area, but the water before or after galvanizing, of so that later the rust “flows” through those points. If it is continuous welding, drainage holes must be left to avoid explosions that affect the safety of the operators, since pockets or air bubbles in a piece submerged in molten Zn at 450º C suppose an instantaneous evacuation of the air causing explosions.
In many pieces destined for galvanizing, the designer must take into account that it is necessary to drill holes at certain points in order to evacuate the Zn during immersion in the crucible. For this, the best option is to contact the galvanizer by sending him the drawing of the piece. , for a professional to tell you where to do it. This depends on how the material to be galvanized is hung during the process.
In the pieces that have holes or closed corners, it is essential to make holes in each and every one of the hollow areas, so that there are no air bubbles and so that the liquid Zn drains completely. Air bubbles can leave “ungalvanized spots” so they are left unprotected.
The cleaner or fat-free the steel, the better it galvanizes, it is an important detail since there are fats that can generate black spots on the piece and are not the responsibility of the galvanizer.
The paints that sometimes appear on steel as residue behave as very persistent elements and the galvanizing process does not eliminate them, so it is essential to remove them manually or proceed to burn them.
If it is necessary to paint after galvanizing, it is always necessary to indicate to the galvanizer that you intend to paint the part next when requesting quotes. In this case, it requires special treatment.
With all these measures, it will be possible to have an excellent preparation of the pieces that are going to be galvanized and will achieve optimum quality with a good finish.
The appearance of galvanizing can vary greatly on all or part of the surface of the pieces depending on the chemical composition of the steel used, its surface condition, the thermal effect of previous treatments such as tempering, annealing… The UNE-EN ISO 1461 standard, in point 6.1 makes it very clear that the presence of darker or lighter areas, or some irregularity should not constitute a reason for rejection. Likewise, stains from wet storage, consisting mainly of Zn oxide, should not be a reason for rejection, provided that the thickness of the generated alloy remains above the specified minimum value”.
If you have to go over or sand the galvanized material, be careful so that the go over or sanding does not remove the Zn layer, or you will lose the protection of the piece.
According to the UNE-EN ISO 1461 Standard, it is specified that the inspection for acceptance is carried out in the hot-dip galvanizing plant, so that the galvanized once the materials have been removed from the factories, are not responsible for the damage caused to the materials due to incorrect handling, transport or storage. For galvanized under other standards this principle is equally applicable.
Prices are always applied to the output weight after galvanizing and on a certified scale.
Corrosivity categories according to the UNE-EN ISO 14713 standard.
UNE-EN ISO 1461 table. Minimum allowable thicknesses of the thickness of the galvanized coating.
