Weld galvanized steel - what do you have to pay attention to?

If you want to weld galvanized steel, you must - apart from the general weldability of the steel - also pay attention to a few other peculiarities. What is fundamental and important in this case in welding is explained in detail in this article.

Protective function of zinc

Galvanized steel has a protective coating of zinc to prevent corrosion. The zinc layer can be applied with very different methods:

  • by so-called hot dip galvanizing (hot dipping method)
  • by means of spray galvanizing
  • by galvanic galvanizing
  • by so-called mechanical galvanizing
  • by the so-called Sherardizing

Due to the large differences in the methods, there are also very different results with regard to the layer thickness, the durability and the load-bearing capacity of the zinc coating. Also, not all zinc plating is equally protective for the steel.

When welding, pay attention

If you want to weld galvanized steel now, you have to pay attention to a few things:

  • basic weldability of the steel must be given
  • Remove zinc layer
  • Restore zinc layer
  • Welding on load bearing steel parts
  • possible problems of the load capacity of the welded joint

Remove zinc layer

The existing zinc layer must be completely removed before welding, otherwise there is a risk of corrosion. The removal usually has to be done by grinding. The problem is the often unknown or underestimated layer thickness of the zinc layer and the risk of corrosion, which occurs when other areas of the workpiece come into contact with the iron-containing grinding dust.

Restore zinc layer

After welding, the original zinc layer must be restored to the same thickness and with the same protective effect. There are precisely defined regulations in DIN 50976 (standard purity, corrosion protection value, minimum layer thickness and proof tests, etc.). Zinc dust coatings or sprays are in almost all cases neither sufficient nor admissible.

Welding on load bearing steel parts

Due to the possible problems with corrosion and a possible reduction in the load-bearing capacity of welded joints (iron-zinc inclusions, pores, soldering, etc.), welding of galvanized load-bearing components is generally prohibited.

Possible problems of the load capacity of the welded joint

In other cases (with non-structural components), the load capacity of the weld can be poor. For example, soldering is a very common problem.

Tips & Tricks

A good way to restore the corrosion protection is a combination of zinc paste and zinc spray (but the zinc spray should at least have a zinc content of 92 - 95%). In most cases, the strict specifications of DIN and the necessary corrosion protection values ​​can be achieved in this way.

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