Study: Electropolishing Improves Welded Areas’ Corrosion Resistance | Limat | 03.11.09


Stainless steel is is used in many industries, the likes of the chemical industry and the foods and pharmacological industries. Stainless steel is particularly popular in these industries because of its excellent corrosion resistance and its chemical makeup, which allows for a variety of uses; as well as its easy maintenance, compared to other metals.

Many types of stainless steel undergo welding in order to suit the various industries' needs. The welding process, however, releases oxides that can affect the temperature-sensitives areas which are adjacent to the welded areas. The chemical composition of this oxides varies and often depends on the exposure temperature, the length of the welding process and overall environment where the process takes place. This differs from natural oxides, whose post-welding composition is constant.

As a result, these metals must undergo electropolishing, or another treatment, in order to recreate a layer of passivation, and remove the oxides from the metals' surfaces. This treatment is vital to the future resistance of the metal.

Recently, a study was commissioned in order to determine which is the best treatment for such metals. The study reviewed corrosion-resistance improvements in metals which were welded, and therefore subjected to the welding process' heat, before undergoing electropolishing.

The study found that gas bubbles appeared on the surface of the metals tested, which appeared in the welding seams. The number of these bubbles, however, reduced  significantly in the metal sample which underwent electropolishing – electrochemical polishing – after being welded. After three days of testing, the welded pieces of metals were removed from their base metals and subjected to a visual test. The latter clearly showed that the parts which underwent electrochemical polishing suffered no damage. The surface of the parts which were not electropolished but dried by compressed air, were cracked – cracks which in three places matured into full dints.

The study concluded that electrochemical polishing is the best way to restore and improve  passivation in welded metals, as well as in their adjacent areas, which are affected by oxides emissions.

To read the full study click here