How welding process influences corrosion? See some good practices!

Corrosion in welds can occur even after choosing suitable fill material, respecting the welding procedures and after obtaining the proper forms. Elements present in the environment accelerates the chemical process that occurs in the material surface, triggering corrosion.

Factors affecting welded elements

Sometimes it`s difficult to determine why corrosion occurs in welds, but the following factors may be related to this case:

• Weldment design
• Fabrication technique
• Welding practice
• Welding sequence
• Moisture contamination
• Organic or inorganic chemical species
• Oxide film and scale
• Weld slag and spatter
• Incomplete weld penetration or fusion
• Porosity
• Cracks (crevices)
• High residual stresses
• Improper choice of filler metal
• Final surface finish

In choosing the best materials, please read the related article classes of corrosion and corrosion resistance. You will form an idea of the steps you can take to reduce the risk of corrosion and ensure long-term effectiveness of the equipment and reduce maintenance costs.

Good practices

Materials selections and consumables required for the welding process - It requires a careful choice of materials, as they may cause differences at micro and macro-compositional. Thus, there are points that favor the appearance of corrosion.

Surface preparation - Cleaning the surface properly can reduce the aggressiveness of the environment. We mention that this process is not so simple. For example, the mechanical cleaning of the surface (blasting) may leave some impurities on the surface. Therefore we encourage this process to be executed by a specialized team.

The welding process - requires removal of slag. If the welding method uses flux, it requires welding points geometry allowing removal of residues, as they are hydrophilic (have potential corrosive).

Applying corrosion protection - method that significantly reduces the risk of corrosion. Protection must cover the entire surface of a metal, including welding points. One point exposed can cause corrosion and extend over the entire surface. This process requires proper preparation.

These are some of the methods you can use to reduce the risk of corrosion. If you want to apply a corrosion protection system, you should take into account that it must be adapted to the environment. Otherwise, the surfaces will be exposed to corrosion. If you a specialized team that can guarantee the quality of the application, just contact us.

Sursa: http://www.asminternational.org/documents/10192/1849770/ACFAB86.pdf